 Table XVI
Mean Vanishing Bearing for Danaus plexippus in East Winds
Descriptive statistics for the September 28 to October 10, 1987,
observations in Calhoun, Georgia
|
Statistic |
Value |
Comments |
1)
Sample size |
7 |
Records with non-numerical records for
vanishing bearing or wind (e.g. N instead of 360°) were not included in
the analysis. |
2) Sum of
sines |
-6.87388 |
Divide by sample size to get mean sine (line 4). Also
needed when pooling data from other studies. |
3) Sum of
cosines |
+0.47642 |
Divide by sample size to get mean cosine (line 5).
Also needed when pooling data from other studies. |
4) Mean sine |
-0.98198 |
Values for lines 4 and 5 are used with
sample size (line 1) to calculate length of mean vector (line 6). |
5) Mean cosine |
+0.06806 |
6)
Length of mean vector |
0.98434 |
An index of dispersal of
bearings. Used to determine values for lines 9 and 13. |
7) Sine of
mean vector |
-0.99761 |
Values for lines 7 and 8 are obtained by
dividing the values from lines 4 and 5 by the value for line 6. The resulting
sine and cosine are used with a Trigonometry Table of sines and cosines to
extrapolate the angle of the mean vector, in this case the Magnetic mean bearing (line10
). |
8) Cosine of
mean vector |
-0.06914 |
9) Angular
deviation |
±11.5° |
Determined from Tables that convert mean vector length
(line 6) into angular deviation (or circular standard deviation). |
10)
Magnetic mean bearing |
274° ±11.5°
(West) |
Descriptive statistic for the True mean
bearing and the dispersion around the mean for the sample. |
11) Magnetic declination
|
-2ºW |
Subtract magnetic declination (variation) to obtain True
bearing |
12) True
mean bearing |
272° ±11.5°
(West) |
Descriptive statistic for the True mean
bearing and the dispersion around the mean for the sample. |
13) 95% confidence
intervals |
±10° |
95% Confidence Intervals (C.I.) are extrapolated from a
chart using values from lines 1 and 6. |