Fig. 5. Histograms of directional angles considered to be true North (0°) under weather situations A 1; B, C 2; D, E 3; F, G 4. Dashed arrows mark the directions of the mean vectors. The number of individual orientations N, the direction of the mean vector a with 95% confidence limits, the length of the mean vector r and the significance level p of the Rayleigh test for uniformity of distribution of the measured directions are given in the lower half of the dials. A–E The distributions of direction considered as North are significantly directional under weather situations 1, 2, and 3; F and G while they are uniform under weather situation 2 4. E and G the test values rand significance levels p of circular rank correlation tests mark significant correlations between directional angles identified as true North by the observer using the sunstone and shadow-stick, and D and F between their unaided guesses.
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