 Table II g
Descriptive statistics of the September
29, 1987 Observations of the Danaus plexippus migration in Calhoun, Georgia
|
Statistic |
Value |
Comments |
1)
Sample size |
22 |
Four obserations of migrants of
other butterfly species were not included in the analysis. |
2) Sum of
sines |
-18.55707 |
Divide by sample size to get mean sine (line 4). Also
needed when pooling data from other studies. |
3) Sum of
cosines |
+8.92658 |
Divide by sample size to get mean cosine (line 5).
Also needed when pooling data from other studies. |
4) Mean sine |
-0.84350 |
Values for lines 4 and 5 are used with
sample size (line 1) to calculate length of mean vector (line 6). |
5) Mean cosine |
+0.40575 |
6)
Length of mean vector |
0.93602 |
An index of dispersal of
bearings around mean bearing. Used to determine values for lines 9 and
13. |
7) Sine of
mean vector |
-0.90116 |
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 |
+0.43349 |
9) Angular
deviation |
±19.9° |
Determined from Tables that convert mean vector length
(line 6) into angular deviation (or circular standard deviation). |
10)
Magnetic mean bearing |
295.5° ±19.9°
(Northwest) |
Descriptive statistic of 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 |
293.5° ±19.9°
(Northwest) |
Descriptive statistic for the True mean
bearing and the dispersion around the mean for the sample. |
13) 95% confidence
intervals |
±8° |
Values from lines 1 and 6 are used to extrapolate 95% (or
99%) Confidence Intervals (C.I.) from appropriate Tables. |