Alan B. Forsythe

Bio: Alan B. Forsythe is an academic researcher from University of California, Los Angeles. The author has contributed to research in topics: Population & Brown–Forsythe test. The author has an hindex of 27, co-authored 63 publications receiving 5820 citations.

Robust Tests for the Equality of Variances

Abstract: Alternative formulations of Levene's test statistic for equality of variances are found to be robust under nonnormality. These statistics use more robust estimators of central location in place of the mean. They are compared with the unmodified Levene's statistic, a jackknife procedure, and a χ2 test suggested by Layard which are all found to be less robust under nonnormality.

The Small Sample Behavior of Some Statistics Which Test the Equality of Several Means

Abstract: Four statistics which may be used to test the equality of population means are com-pared with respect to their robustness under heteroscedasticity, their power, and the overlap of their critical regions. The four are: the ANOVA F-statistic; a modified F which has the same numerator as the ANOVA but an altered denominator; and two similar statistics proposed by Welch and James which differ primarily in their approximations for their critical values. The critical values proposed by Welch are a better approximation for small sample sizes than that proposed by James. Both Welch's statistic and the modified F are robust under the inequality of variances. The choice between them depends upon the magnitude of the means and their standard errors. When the population variances are equal, the critical region of the modified F more closely approximates that of the ANOVA than does Welch's.

Somatization in the Community

Abstract: • We examined the prevalence of somatization disorder symptoms elicited with the Diagnostic Interview Schedule in 3132 community respondents interviewed in Los Angeles by the Epidemiologic Catchment Area program. The variables age, gender, ethnic background, and the presence of a psychiatric diagnosis significantly influenced the number of somatization symptoms reported. An introductory review on conceptual and nosological aspects of somatization phenomena led to the formulation of a less-restrictive operational definition of the somatizer. We found that 4.4% of the respondents met criteria for this abridged cutoff score of somatization, whereas only 0.03% of the respondents met criteria for the fullDSM-IIIsomatization disorder diagnosis. This abridged cutoff score was associated with sociodemographic factors and psychiatric diagnosis in the direction predicted.

372: The Anova and Multiple Comparisons for Data with Heterogeneous Variances

Abstract: The lack of robustness of the one-way ANOVA to the heterogeneity of the within group variances is well-known (Scheffe [1959]). For two samples a robust version of the t-test has been developed (Welch [1947], Wang [1971]). For more than two samples Welch [1951] proposed a statistic based on an asymptotic confidence interval approach. An alternative robust method is to replace the denominator of the usual ANOVA F-statistic by an estimate of the variance of the numerator (Brown and Forsythe [1974]). Here we show how this latter statistic can be derived by combining individual orthonormal contrasts. This result is extended to the analysis of a two-way ANOVA and to test the lack of fit of contrasts partitioned from the mode]. A multiple comparisons test procedure is proposed which is similar to that of Scheffe [1959].

Pharmacological interventions for somatoform disorders in adults.

Abstract: BACKGROUND: Somatoform disorders are characterised by chronic, medically unexplained physical symptoms (MUPS). Although different medications are part of treatment routines for people with somatoform disorders in clinics and private practices, there exists no systematic review or meta-analysis on the efficacy and tolerability of these medications. We aimed to synthesise to improve optimal treatment decisions.OBJECTIVES: To assess the effects of pharmacological interventions for somatoform disorders (specifically somatisation disorder, undifferentiated somatoform disorder, somatoform autonomic dysfunction, and pain disorder) in adults.SEARCH METHODS: We searched the Cochrane Depression, Anxiety and Neurosis Review Group's Specialised Register (CCDANCTR) (to 17 January 2014). This register includes relevant randomised controlled trials (RCTs) from The Cochrane Library (all years), MEDLINE (1950 to date), EMBASE (1974 to date), and PsycINFO (1967 to date). To identify ongoing trials, we searched ClinicalTrials.gov, Current Controlled Trials metaRegister, the World Health Organization International Clinical Trials Registry Platform, and the Chinese Clinical Trials Registry. For grey literature, we searched ProQuest Dissertation {\&} Theses Database, OpenGrey, and BIOSIS Previews. We handsearched conference proceedings and reference lists of potentially relevant papers and systematic reviews and contacted experts in the field.SELECTION CRITERIA: We selected RCTs or cluster RCTs of pharmacological interventions versus placebo, treatment as usual, another medication, or a combination of different medications for somatoform disorders in adults. We included people fulfilling standardised diagnostic criteria for somatisation disorder, undifferentiated somatoform disorder, somatoform autonomic dysfunction, or somatoform pain disorder.DATA COLLECTION AND ANALYSIS: One review author and one research assistant independently extracted data and assessed risk of bias. Primary outcomes included the severity of MUPS on a continuous measure, and acceptability of treatment.MAIN RESULTS: We included 26 RCTs (33 reports), with 2159 participants, in the review. They examined the efficacy of different types of antidepressants, the combination of an antidepressant and an antipsychotic, antipsychotics alone, or natural products (NPs). The duration of the studies ranged between two and 12 weeks.One meta-analysis of placebo-controlled studies showed no clear evidence of a significant difference between tricyclic antidepressants (TCAs) and placebo for the outcome severity of MUPS (SMD -0.13; 95{\%} CI -0.39 to 0.13; 2 studies, 239 participants; I(2) = 2{\%}; low-quality evidence). For new-generation antidepressants (NGAs), there was very low-quality evidence showing they were effective in reducing the severity of MUPS (SMD -0.91; 95{\%} CI -1.36 to -0.46; 3 studies, 243 participants; I(2) = 63{\%}). For NPs there was low-quality evidence that they were effective in reducing the severity of MUPS (SMD -0.74; 95{\%} CI -0.97 to -0.51; 2 studies, 322 participants; I(2) = 0{\%}).One meta-analysis showed no clear evidence of a difference between TCAs and NGAs for severity of MUPS (SMD -0.16; 95{\%} CI -0.55 to 0.23; 3 studies, 177 participants; I(2) = 42{\%}; low-quality evidence). There was also no difference between NGAs and other NGAs for severity of MUPS (SMD -0.16; 95{\%} CI -0.45 to 0.14; 4 studies, 182 participants; I(2) = 0{\%}).Finally, one meta-analysis comparing selective serotonin reuptake inhibitors (SSRIs) with a combination of SSRIs and antipsychotics showed low-quality evidence in favour of combined treatment for severity of MUPS (SMD 0.77; 95{\%} CI 0.32 to 1.22; 2 studies, 107 participants; I(2) = 23{\%}).Differences regarding the acceptability of the treatment (rate of all-cause drop-outs) were neither found between NGAs and placebo (RR 1.01, 95{\%} CI 0.64 to 1.61; 2 studies, 163 participants; I(2) = 0{\%}; low-quality evidence) or NPs and placebo (RR 0.85, 95{\%} CI 0.40 to 1.78; 3 studies, 506 participants; I(2) = 0{\%}; low-quality evidence); nor between TCAs and other medication (RR 1.48, 95{\%} CI 0.59 to 3.72; 8 studies, 556 participants; I(2) =14{\%}; low-quality evidence); nor between antidepressants and the combination of an antidepressant and an antipsychotic (RR 0.80, 95{\%} CI 0.25 to 2.52; 2 studies, 118 participants; I(2) = 0{\%}; low-quality evidence). Percental attrition rates due to adverse effects were high in all antidepressant treatments (0{\%} to 32{\%}), but low for NPs (0{\%} to 1.7{\%}).The risk of bias was high in many domains across studies. Seventeen trials (65.4{\%}) gave no information about random sequence generation and only two (7.7{\%}) provided information about allocation concealment. Eighteen studies (69.2{\%}) revealed a high or unclear risk in blinding participants and study personnel; 23 studies had high risk of bias relating to blinding assessors. For the comparison NGA versus placebo, there was relatively high imprecision and heterogeneity due to one outlier study. Although we identified 26 studies, each comparison only contained a few studies and small numbers of participants so the results were imprecise.AUTHORS' CONCLUSIONS: The current review found very low-quality evidence for NGAs and low-quality evidence for NPs being effective in treating somatoform symptoms in adults when compared with placebo. There was some evidence that different classes of antidepressants did not differ in efficacy; however, this was limited and of low to very low quality. These results had serious shortcomings such as the high risk of bias, strong heterogeneity in the data, and small sample sizes. Furthermore, the significant effects of antidepressant treatment have to be balanced against the relatively high rates of adverse effects. Adverse effects produced by medication can have amplifying effects on symptom perceptions, particularly in people focusing on somatic symptoms without medical causes. We can only draw conclusions about short-term efficacy of the pharmacological interventions because no trial included follow-up assessments. For each of the comparisons where there were available data on acceptability rates (NGAs versus placebo, NPs versus placebo, TCAs versus other medication, and antidepressants versus a combination of an antidepressant and an antipsychotic), no clear differences between the intervention and comparator were found.Future high-quality research should be carried out to determine the effectiveness of medications other than antidepressants, to compare antidepressants more thoroughly, and to follow-up participants over longer periods (the longest follow up was just 12 weeks). Another idea for future research would be to include other outcomes such as functional impairment or dysfunctional behaviours and cognitions as well as the classical outcomes such as symptom severity, depression, or anxiety.

Utility of a New Procedure for Diagnosing Mental Disorders in Primary Care: The PRIME-MD 1000 Study

Abstract: Objective. —To assess the validity and utility of PRIME-MD (Primary Care Evaluation of Mental Disorders), a new rapid procedure for diagnosing mental disorders by primary care physicians. Design. —Survey; criterion standard. Setting. —Four primary care clinics. Subjects. —A total of 1000 adult patients (369 selected by convenience and 631 selected by site-specific methods to avoid sampling bias) assessed by 31 primary care physicians. Main Outcome Measures. —PRIME-MD diagnoses, independent diagnoses made by mental health professionals, functional status measures (Short-Form General Health Survey), disability days, health care utilization, and treatment/ referral decisions. Results. —Twenty-six percent of the patients had a PRIME-MD diagnosis that met full criteria for a specific disorder according to the Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition . The average time required of the primary care physician to complete the PRIME-MD evaluation was 8.4 minutes. There was good agreement between PRIME-MD diagnoses and those of independent mental health professionals (for the diagnosis of any PRIME-MD disorder, κ=0.71; overall accuracy rate=88%). Patients with PRIME-MD diagnoses had lower functioning, more disability days, and higher rates of health care utilization than did patients without PRIME-MD diagnoses (for all measures, P Conclusion. —PRIME-MD appears to be a useful tool for identifying mental disorders in primary care practice and research. ( JAMA . 1994;272:1749-1756)

Robust Tests for the Equality of Variances

Abstract: Alternative formulations of Levene's test statistic for equality of variances are found to be robust under nonnormality. These statistics use more robust estimators of central location in place of the mean. They are compared with the unmodified Levene's statistic, a jackknife procedure, and a χ2 test suggested by Layard which are all found to be less robust under nonnormality.

The Composite International Diagnostic Interview: An Epidemiologic Instrument Suitable for Use in Conjunction With Different Diagnostic Systems and in Different Cultures

Abstract: • The Composite International Diagnostic Interview (CIDI), written at the request of the World Health Organization/US Alcohol, Drug Abuse, and Mental Health Administration Task Force on Psychiatric Assessment Instruments, combines questions from the Diagnostic Interview Schedule with questions designed to elicit Present State Examination items. It is fully structured to allow administration by lay interviewers and scoring of diagnoses by computer. A special Substance Abuse Module covers tobacco, alcohol, and other drug abuse in considerable detail, allowing the assessment of the quality and severity of dependence and its course. This article describes the design and development of the CIDI and the current field testing of a slightly reduced "core" version. The field test is being conducted in 19 centers around the world to assess the interviews' reliability and its acceptability to clinicians and the general populace in different cultures and to provide data on which to base revisions that may be found necessary. In addition, questions to assess International Classification of Diseases , ninth revision, and the revised DSM-III diagnoses are being written. If all goes well, the CIDI will allow investigators reliably to assess mental disorders according to the most widely accepted nomenclatures in many different populations and cultures.