7.92 ● The paper “Temperature and the Northern Distributions of Wintering Birds” (Ecology [1991]:

2274–2285) gave the following body masses (in grams) for 50 different bird species:

7.7 10.1 21.6 8.6 12.0 11.4 16.6 9.4 11.5 9.0 8.2 20.2 48.5 21.6 26.1 6.2 19.1 21.0 28.1 10.6 31.6 6.7 5.0 68.8 23.9 19.8 20.1 6.0 99.6 19.8 16.5 9.0 448.0 21.3 17.4 36.9 34.0 41.0 15.9 12.5 10.2 31.0 21.5 11.9 32.5 9.8 93.9 10.9 19.6 14.5

a. Draw a histogram based on class intervals 5 to ,10, 10 to ,15, 15 to ,20, 20 to ,25, 25 to ,30, 30 to ,40, 40 to ,50, 50 to ,100, and 100 to ,500. Is a transformation of the data desirable? Explain.

b. Use a calculator or statistical computer package to calculate logarithms of these observations, and construct a histogram. Is the log transformation successful in producing a more symmetric distribution?

c. Consider transformed value 5 1

Ïoriginal value and construct a histogram of the transformed data. Does the histogram appear to resemble a normal curve?