Showing papers by "Auckland University of Technology published in 2004"

Stretching and injury prevention: an obscure relationship.

Abstract: It is generally accepted that increasing the flexibility of a muscle-tendon unit promotes better performances and decreases the number of injuries. Stretching exercises are regularly included in warm-up and cooling-down exercises; however, contradictory findings have been reported in the literature. Several authors have suggested that stretching has a beneficial effect on injury prevention. In contrast, clinical evidence suggesting that stretching before exercise does not prevent injuries has also been reported. Apparently, no scientifically based prescription for stretching exercises exists and no conclusive statements can be made about the relationship of stretching and athletic injuries. Stretching recommendations are clouded by misconceptions and conflicting research reports. We believe that part of these contradictions can be explained by considering the type of sports activity in which an individual is participating. Sports involving bouncing and jumping activities with a high intensity of stretch-shortening cycles (SSCs) [e.g. soccer and football] require a muscle-tendon unit that is compliant enough to store and release the high amount of elastic energy that benefits performance in such sports. If the participants of these sports have an insufficient compliant muscle-tendon unit, the demands in energy absorption and release may rapidly exceed the capacity of the muscle-tendon unit. This may lead to an increased risk for injury of this structure. Consequently, the rationale for injury prevention in these sports is to increase the compliance of the muscle-tendon unit. Recent studies have shown that stretching programmes can significantly influence the viscosity of the tendon and make it significantly more compliant, and when a sport demands SSCs of high intensity, stretching may be important for injury prevention. This conjecture is in agreement with the available scientific clinical evidence from these types of sports activities. In contrast, when the type of sports activity contains low-intensity, or limited SSCs (e.g. jogging, cycling and swimming) there is no need for a very compliant muscle-tendon unit since most of its power generation is a consequence of active (contractile) muscle work that needs to be directly transferred (by the tendon) to the articular system to generate motion. Therefore, stretching (and thus making the tendon more compliant) may not be advantageous. This conjecture is supported by the literature, where strong evidence exists that stretching has no beneficial effect on injury prevention in these sports. If this point of view is used when examining research findings concerning stretching and injuries, the reasons for the contrasting findings in the literature are in many instances resolved.

Power and resistance in the implementation of a medical management information system

Abstract: . This paper presents an analysis of the implementation of a large information system in a New Zealand hospital. The system was intended to monitor and scrutinize clinical activity, and management hoped to influence clinical behaviour through the increased visibility afforded by the system. However, doctors were not the passive subjects of a computerized control system, and some were able to resist the application of the information produced by challenging its validity or using it to argue for more resources. Nevertheless, the interrelatedness of the information system with the organizational forms and practices within which it was used and which it helped shape reinforced the concepts, norms and values associated with the new management and economic discourse prevalent in the hospital, and helped to produce more defined accountabilities for doctors. With time, the role of the information system was reinterpreted, and in the face of continued resistance by doctors, it was relegated to a less significant role. The potential for engendering self-disciplining behaviour in organizational participants through the pervasive, everyday use of the information the system produced likewise diminished.

Ethical Investing in Australia; Is there a Financial Penalty?

Abstract: This study provides new evidence on the performance and investment style of retail ethical funds in Australia. By applying a conditional multi-factor Carhart (1997) model, we solve the benchmark problem most prior ethical studies suffered from. After controlling for investment style, time-variation in betas, bond exposure and home bias, we observe no evidence of significant differences in risk-adjusted returns between ethical and conventional funds during the 1992-2003 period. This result however is sensitive to the chosen time period. During 1992-1996, domestic ethical funds under-perform their conventional counterparts significantly. During 1996-2003, the ethical funds match the performance of conventional funds more closely. This suggests there is a learning effect for the relatively young ethical investment industry.

Online consumer trust: a multi-dimensional model

Abstract: Consumer trust is widely heralded as an essential element for the success of electronic commerce, yet the concept itself is still clouded in confusion by the numerous definitions and points of view held across multiple disciplines. It is the aim of this paper to synthesise the viewpoints from across the disciplines and bring them together in a multi-dimensional trust model. It is hoped that in doing so, these broad assortment of views will highlight the true underlying nature of trust in the online environment. From these multiple disciplines, three dimensions of trust emerged: dispositional trust, institutional trust and interpersonal trust, each bringing its own influencing factors into the overall intention to trust. From this model emerged the notion that the consumer as an individual is central to the understanding of trust, and in turn that the individual’s personality and culture form the foundation for the development of trust.

Reliability and validity of a linear position transducer for measuring jump performance.

Abstract: This study determined the reliability and validity of a linear position transducer to measure jump performance by comparing the mean force, peak force, and time-to-peak force measurements with data obtained simultaneously with a force platform. Twenty-five men performed squat, countermovement, and drop jumps with the linear transducer connected from a waist belt and base, which were placed upon a force platform. The Pearson correlation coefficients across the 3 jumps for the mean force (r = 0.952-0.962), peak force (r = 0.861-0.934), and time-to-peak force (r = 0.924-0.995) were high, providing evidence that the linear-transducer and force-platform measurements were similar. The trial-to-trial reliability of the jumps measured by the linear position transducer gave an intraclass correlation coefficient of 0.924-0.975 for mean force, 0.977-0.982 for peak force, and 0.721-0.964 for time-to-peak force. The coefficients of variation were 2.1-4.5% for mean force, 2.5-8.4% for peak force, and 4.1-11.8% for time-to-peak force. Our findings showed that the calculations derived from the linear transducer were very similar to those of the force platform and hence provided evidence of the validity of this method. The data from the linear transducer were also shown to be reliable. Therefore, this method of calculating force may provide a cost-effective alternative to the force platform for measuring this variable.

Progression and variability of competitive performance of Olympic swimmers

Abstract: Estimates of progression and variability of athletic performance in competitions are useful for researchers and practitioners interested in factors that affect performance. We used repeated-measures mixed modelling to analyse 676 official race times of 26 US and 25 Australian Olympic swimmers in the 12-month period leading up to the 2000 Olympic Games. Progression was expressed as percent changes in mean performance; variability was expressed as the coefficient of variation in performance of an individual swimmer between races. Within competitions, both nations showed similar improvements in mean time from heats through finals (overall 1.2%; 95% confidence limits 1.1 to 1.3%). Mean competition time also improved over 12 months by a similar amount in both nations (0.9%; 95% confidence limits 0.6 to 1.2%). The US swimmers showed a greater improvement between the finals (a difference of 0.5%; 95% confidence limits −0.2 to 1.1%), which paralleled changes in the medal haul of the two nations. The coefficient o...

Body size, body composition, and fat distribution: a comparison of young New Zealand men of European, Pacific Island, and Asian Indian ethnicities.

Abstract: Aims To investigate body size and body fat relationships and fat distribution in young healthy men drawn from New Zealand European, Pacific Island, and Asian Indian populations. Method A total of 114 healthy men (64 European, 31 Pacific Island, 19 Asian Indian) aged 17–30 years underwent measurements of height, weight, and body composition by total body dual-energy X-ray absorptiometry (DXA). Body mass index (BMI) was then calculated. Percent body fat (%BF), fat-free mass, bone mineral content, bone mineral density, abdominal fat, thigh fat, and appendicular skeletal muscle mass (ASMM) were obtained from the DXA scans. Results For the same BMI, %BF for Pacific Island men was 4% points lower and for Asian Indian men was 7–8% points higher compared to Europeans. Compared to European men for the same %BF, BMI was 2–3 units higher for Pacific Island, and 3– 6 units lower for Asian Indian. The ratio of abdominal fat to thigh fat, adjusted for height, weight, and %BF, was significantly higher for Asian Indian men than European (p=0.022) and Pacific Island (p=0.002) men. ASMM, adjusted for height and weight, was highest in Pacific Island and lowest in Asian Indian men. Conclusions The relationship between %BF and BMI is different for European, Pacific Island, and Asian Indian men which may, at least in part, be due to differences in muscularity. Asian Indians have more abdominal fat deposition than their European and Pacific Island counterparts. Use of universal BMI cut-off points are not appropriate for comparison of obesity prevalence between these ethnic groups. It is widely recognised that obesity (defined as an excess of body fat) and obesityrelated diseases are an increasing global problem now reaching epidemic proportions. 1 Because of its general use and ease of measurement, body mass index (BMI) is commonly used as a surrogate measure for obesity. The World Health Organization (WHO) cut-off point for classification of obesity as a body mass index (BMI) above 30 kg/m 2 is intended as an internationally useful threshold for reflecting risk for Type 2 diabetes and cardiovascular diseases. Based on this cut-off, Asian immigrants from the Indian subcontinent have low rates of obesity yet, relative to Europeans, they have a higher prevalence of coronary heart

Passive force, angle, and stiffness changes after stretching of hamstring muscles.

Abstract: REID, D. A., and P. J. MCNAIR. Passive Force, Angle, and Stiffness Changes after Stretching of Hamstring Muscles. Med. Sci. Sports Exerc., Vol. 36, No. 11, pp. 1944–1948, 2004. Periodic or long-term stretching programs have demonstrated changes in joint range of motion. The suggested mechanisms for these increases in range of motion are changes in the tissue properties of the muscle and more recently stretch tolerance. However, few studies have examined changes in passive resistive forces and related these changes to increases in range of motion. Purpose: The purpose of this study was to investigate the influence of a 6-wk hamstring-stretching program on knee extension range of motion, passive resistive forces, and muscle stiffness. Methods: A randomized control trial with repeated measures was undertaken with 43 school-age subjects. Hamstring extensibility was assessed by a passive knee extension test using a Kincom® isokinetic dynamometer. The intervention group participated in a 6-wk hamstring-stretching program. Stretches were performed 5 d·wk 1 , once per day, held for 30 s, and for 3 repetitions. The control group did not stretch over the 6-wk intervention period. Measurements of hamstring extensibility were repeated at the end of the 6-wk intervention. Results: After the intervention period, significant (P 0.05) increases in knee extension range of motion, passive resistive force, and stiffness were observed in the experimental group. No significant differences were observed in the control group’s findings for the same variables. Conclusions: The findings of this study are consistent with other literature that shows periodic stretching programs over a 6-wk time frame produce significant changes in knee extension range of motion. The finding of increased stiffness in the new range of motion, gained as a result of the stretching program, provides some evidence that structural changes had occurred in the stretched muscles. Key Words: HAMSTRING STRETCHING, VISCOELASTICITY, FLEXIBILITY, TRAINING, CHILDREN

Why older Australians participate in exercise and sport.

Abstract: Research on variables that encourage older adults to exercise is limited. This study was carried out to identify the participation motives of older Australians involved in regular exercise and sport. The 815 participants (399 men, 416 women) ranged in age from 55 to 93 years (M = 63.6, SD = 7.8) and were participating in their activities of choice at least once per week. All participants completed the Participation Motivation Questionnaire for Older Adults. The most common exercise/sport activities that participants were involved in were walking, golf, lawn bowls, tennis, and swimming. The most highly reported motives for participation were to keep healthy, liking the activity, to improve fitness, and to maintain joint mobility. Principal-components analysis of the questionnaire revealed 6 factors: social, fitness, recognition, challenge/benefits, medical, and involvement. Analyses of variance showed significant differences in reasons for participation in exercise and sport based on gender, age, education...

Blood group terminology 2004: from the International Society of Blood Transfusion committee on terminology for red cell surface antigens.

Abstract: 1 Bristol Institute for Transfusion Sciences, Bristol, UK 2 Growing your Knowledge, Spit Junction, NSW, Australia 3 American Red Cross Blood Services, Los Angeles-Orange Counties Region, Los Angeles, CA, USA 4 Biotechnology Research Centre, Auckland University of Technology, Auckland, New Zealand 5 Regional Blood Transfusion Center, Department of Clinical Immunology, University Hospital, Arhus N, Denmark 6 Department of Pathology, University Hospitals UH-2G332, Ann Arbor, Michigan, USA 7 Reference Laboratory for Immunohematology and Blood Groups, National Blood Services Centre, Tel Hashomer, Israel 8 New York Blood Center, New York, NY, USA 9 Ortho-Clinical Diagnostics, Raritan, NJ, USA 10 Drexel University College of Medicine, Philadelphia, PA, USA 11 Gamma Biologicals Inc (subsidiary of Immunocor Inc), Houston, TX, USA 12 Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, Amsterdam, the Netherlands 13 Centre national de Reference pour les Groupes sanguines (CNTS), Paris, France 14 International Blood Group Reference Laboratory, Bristol, UK 15 Finnish Red Cross Blood Transfusion Service, Helsinki, Finland 16 South African National Blood Service, East Coast Region, Pinetown, South Africa 17 Osaka Red Cross Blood Center, Osaka, Japan 18 Blood Bank, Hospital Sirio-Libanes, Sao Paulo, Brazil 19 Rh Laboratory, University of Manitoba, Winnipeg, Manitoba, Canada

Comparing the New Zealand and Swedish National Surveys of Gambling and Problem Gambling

Abstract: National surveys of gambling and problem gambling have recently been completed in New Zealand and Sweden. These studies are unique in that data collection was undertaken by official government statistical agencies, involved large, nationally representative samples, and attained high response rates. Comparison of the findings is facilitated by the use of similar procedures and instrumentation and is of interest in that both countries have similar per capita gambling expenditure and welfare states that have recently undergone major economic and social restructuring. Data on gambling participation, problem gambling prevalence and risk factors for problem gambling are presented and discussed. While there are a number of similarities and differences, the Swedish findings are more similar to those of an earlier national survey conducted in New Zealand during 1991. This suggests that risk factors are changing over time in relation to evolving patterns of gambling participation and attitudes towards gambling, a finding that has implications for future patterns of gambling and problem gambling in these and other countries.

A prospective study of problem and regular nonproblem gamblers living in the community.

Abstract: Little is known about the life course of gambling problems and there have been no prospective studies of problem gambling. This article describes a study of 77 problem gamblers and 66 nonproblem gamblers recruited from a national prevalence survey in New Zealand in 1991 and reassessed in 1998. While most 1991 problem gamblers were nonproblematic at follow-up, a significant minority had developed more serious problems. Multiple logistic regression analysis identified more severe gambling problems, hazardous drinking, and a preference for track betting as the strongest independent predictors of subsequent problem gambling. These findings contradict conventional notions that pathological gambling is invariably a chronic or chronically relapsing disorder. The findings have implications for the interpretation of previous research, conduct of future research, and problem gambling policy and treatment.

Towards an ideal rowing technique for performance : the contributions from biomechanics.

Abstract: At international standard, sculling (two oars) and rowing (one oar) are competed on-water over 2000m. Race time is the critical measure of performance and is determined from mean skiff velocity during a race. Although a high proportion of race training is completed on-water, rowing ergometers are commonly used for performance testing, technique coaching, crew selection or for training during poor weather. Rowing biomechanics research has aimed to identify characteristics of successful sculling and sweep rowing strokes; however, biomechanical predictors of 2000m rowing performance are indistinct in the literature. If specific biomechanical parameters distinguish between ability levels and successful or unsuccessful techniques, these attributes can be considered when modifying technique or predicting future rowing performance. The kinematics and kinetics of the sculling and rowing movements have been described on ergometers, on-water and for novice and elite male and female rowers, but there is limited research on the ideal technique or how a rower’s anthropometry or boat set-up could help improve/optimise their rowing performance. Currently viewing the technique and providing verbal feedback is the primary tool used by a coach to help improve a rower’s technique and performance. The greater use of customised telemetered sensors on the rowing skiff can assist the coach and biomechanist with judging when performance (skiff velocity) improves with some form of intervention.

Circulatory volume expansion therapy for aneurysmal subarachnoid haemorrhage.

Abstract: BACKGROUND Secondary ischaemia is a frequent complication after aneurysmal subarachnoid haemorrhage (SAH), and responsible for a substantial proportion of patients with poor outcome after SAH. The cause of secondary ischaemia is unknown, but hypovolaemia and fluid restriction are important risk factors. Therefore, volume expansion therapy (hypervolaemia) is frequently used in patients with SAH to prevent or treat secondary ischaemia. OBJECTIVES To determine the effectiveness of volume expansion therapy for improving outcome in patients with aneurysmal SAH. SEARCH STRATEGY We searched the Cochrane Stroke Group Trials Register (last searched September 2003). In addition we searched MEDLINE (1966 to January 2004) and EMBASE (1980 to January 2004) and contacted trialists to identify further published and unpublished studies. SELECTION CRITERIA All randomised controlled trials of volume expansion therapy in patients with aneurysmal SAH. We also sought controlled trials based on consecutive groups of patients quasi-randomly allocated to treatment or control group and included these in the analysis if the two groups were well comparable with regard to major prognostic factors. DATA COLLECTION AND ANALYSIS Two reviewers independently extracted the data and assessed trial quality. Trialists were contacted to obtain missing information. MAIN RESULTS We identified three trials. One truly randomised trial and one quasi-randomised trial with comparable baseline characteristics for both groups were included in the analyses. Volume expansion therapy did not improve outcome (Relative Risk (RR) 1.0; 95% Confidence Interval (CI) 0.5 to 2.2), nor the occurrence of secondary ischaemia (RR 1.1; 95% CI 0.5 to 2.2). Hypervolaemia tended to increase the rate of complications (RR 1.8; 95% CI 0.9 to 3.7) In another quasi-randomised trial, outcome assessment was done only at the day of operation (7 to 10 days after SAH). In the period before operation, treatment resulted in a reduction of secondary ischaemia (RR 0.33; 95% CI 0.11 to 0.99) and case fatality (RR 0.20; 95% CI 0.07 to 1.2). REVIEWERS' CONCLUSIONS The effects of volume expansion therapy have been studied properly in only two trials of patients with aneurysmal SAH, with very small numbers. At present, there is no sound evidence for the use of volume expansion therapy in patients with aneurysmal SAH.

Factor analysis of barriers to treatment for problem gambling.

Abstract: Attitudes toward problem gambling treatment were investigated in a telephone survey of 1,203 persons in Central Queensland Australia (598 women and 605 men, mean age = 45.8 years). Survey items were compiled from existing substance abuse questionnaires (Center on Alcoholism, Substance Abuse and Addictions, 1995; Sobell et al., 1991). An exploratory factor analysis identified five potential barriers to treatment, including: availability, stigma, cost, uncertainty, and avoidance. Relative to those with few problems, respondents who had numerous gambling problems were more concerned about treatment costs, and the availability and effectiveness of treatment. In addition to the above concerns, older persons more often negatively judged the treatment seeker. In contrast, educated respondents had generally more positive attitudes towards problem gamblers and treatment seeking.

A fuzzy ontology for medical document retrieval

Abstract: Ontologies represent a method of formally expressing a shared understanding of information, and have been seen by many authors as a prerequisite for the "Semantic web". A mapping between query terms and members of an ontology is usually a key part of any ontology enhanced searching tool. However the relative importance of a particular mapping to an overloaded term may be different for different users, and this information is vital for accurate satisfaction of a query.One way of overcoming this problem is the postulation of a "fuzzy ontology". By adding a value for degree of membership to each term that is "overloaded", for each user or group of users then the recovered documents from ontology mediated search can reflect the likely information need. The author will discuss means of ontology fuzzification, by both analysis of a corpus of documents and the use of a relevance feedback mechanism and some possible extensions to this scheme.

Relationship between world-ranking and Olympic performance of swimmers

Abstract: Coaches believe world-ranking lists are a reliable tool for predicting international swimming performance. To examine the relationship between world-ranking and Olympic performance, we modelled world-ranking time and best time from the 2000 Olympic Games for 407 top-50 world-ranked swimmers. Analysis of log-transformed times yielded within-athlete and between-athlete coefficients of variation (CV) and percent changes in performance from world-rankings to Olympics. Variations and performance progressions were compared across sex, stroke, distance, nation and medal status. The within-athlete coefficient of variation of performance for all swimmers was 0.8% (95% confidence limits: 0.7 to 0.9%). Females were slightly less consistent, although not substantially different to males (ratio of female/male within-athlete CV: 1.1; 95% confidence limits: 1.0 to 1.2) and had a wider range of talent (ratio of female/male between-athlete CV: 1.2; 95% confidence limits: 1.1 to 1.4). Swimmers from Australia (AUS) were mor...

Maximal strength and power assessment in novice weight trainers.

Abstract: The purpose of this study was to investigate whether changes in maximal strength and power output occurred over time in the absence of strength and power training in novice weight trainers. It also investigated whether differences existed between upper- and lower-body assessments and unilateral and bilateral assessments. The power output and maximal strength (1 repetition maximum [1RM]) of 10 male novice subjects were measured on 4 occasions, each assessment 7-10 days apart. The exercises used to measure the upper- and lower-body strength and power outputs were the bench press and supine squat, respectively. Significant (p < 0.05) changes in unilateral (9.8-16.8%) and bilateral 1RM (6.8-15.0%) leg strength were found, the first assessment being significantly different from all other assessments and assessment 2 significantly different from assessment 4. Changes in the upper body (10-13.6%) were also observed. The only significant difference was between assessment 1 and the other testing occasions. No differences in power output were observed for both the upper and lower body during the study. It would seem that considerable changes in maximal strength occur rapidly and in the absence of any formal strength training program in novice weight trainers.

On the scalability of fixed broadband wireless access network deployment

Abstract: Fixed broadband wireless access systems, such as the local multipoint distribution service, use an open system architecture that supports a scalable solution for the Internet services over IEEE 802.16 wireless networks. This article presents an overview of various features of BWA systems toward realizing a high level of scalability to support a potentially fast expanding network. This is achieved by optimizing various network resources, which include utilizing the available bandwidth efficiency, making a minor enhancement to an existing system that minimizes the disruption to network services during the network expansion process, and combining the benefits of different features to increase network capacity.

Ethnicity and body fatness in New Zealanders

Abstract: In light of alarming rises in the prevalence of obesity worldwide, tackling the obesity ‘epidemic’ is now a national health priority in many countries. Increasingly, population measures that provide accurate estimates of body fatness are required to assist public health organisations in identifying at-risk groups and developing appropriate preventative strategies. Body mass index (BMI) remains the most costeffective and practical tool in this regard. The World Health Organization (WHO) has issued universal BMI standards for defining ‘overweight’ and ‘obesity’ in adults (BMI =25 kg.m -2 , and =30 kg.m -2 , respectively) based on the risk of obesity-related disease in Europeans. Although widely used, there is mounting evidence suggesting that these standards are not appropriate for all populations. Research indicates that the associations between BMI, percent body fat (%BF), and health risks can vary across different ethnicities. Accordingly, ethnic-specific and country-specific BMI cut-offs for overweight and obesity may be necessary to attain valid prevalence estimates. In New Zealand, this area is largely unexplored in both young people and Asian populations. There is a need for large-scale longitudinal studies investigating the relationships between excessive body fatness and related health outcomes across all major ethnic groups in New Zealand. The obesity epidemic The prevalence of obesity has rapidly reached epidemic proportions in both developed and developing countries around the world. The World Health Organization (WHO) estimates that there are now more than 300 million obese people worldwide—an

Application of ANN with extracted parameters from an electronic nose in cigarette brand identification

Abstract: The Chinese cigarette industry is losing millions of dollars per year due to counterfeit cigarettes. Detecting illegal cigarettes in the field is difficult, but may be possible using portable electronic noses (E-noses). However, the differences between odours from counterfeit and genuine cigarettes are small and detection may prove difficult. In this study we propose a practical approach to increase the performance of E-noses in cigarette brand identification. A portable E-nose was employed to collect and classify aroma signals from different brands of cigarettes. Artificial neural networks (ANNs) were employed and trained with raw data and extracted features from the data collected by the E-nose to identify the cigarettes. This preliminary investigation succeeded in identifying four different types of cigarettes in the laboratory. The identification results obtained from the neural network trained with extracted parameters were better than the ones obtained directly from the E-nose.

A novel feature selection method to improve classification of gene expression data

Abstract: This paper introduces a novel method for minimum number of gene (feature) selection for a classification problem based on gene expression data with an objective function to maximise the classification accuracy. The method uses a hybrid of Pearson correlation coefficient (PCC) and signal-to-noise ratio (SNR) methods combined with an evolving classification function (ECF). First, the correlation coefficients between genes in a set of thousands, is calculated. Genes, that are highly correlated across samples are considered either dependent or co-regulated and form a group (a cluster). Signal-to-noise ratio (SNR) method is applied to rank the correlated genes in this group according to their discriminative power towards the classes. Genes with the highest SNR are used in a preliminary feature set as representatives of each group.An incremental algorithm that consists of selecting a minimum number of genes (variables) from the preliminary feature set, starting from one gene, is then applied for building an optimum classification system. Only variables, that increase the classification rate in each of the validation iteration, are selected and added to the final feature set. The results show that the proposed hybrid PCC, SNR and ECF method improves the feature selection process in terms of number of variables required and also improves the classification rate. The classification accuracy of the ECF classifier is tested through the leave one out method for validation.