Ecologists have long been interested in factors that might explain how far north or south particular animal species are found. As part of one such study, 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 that had previously been thought to have northern boundaries corresponding to a particular isotherm:

14.5

a. Construct a stem-and-leaf display in which 448.0 is shown beside the display as an outlier value, the stem of an observation is the tens digit, the leaf is the ones digit, and the tenths digit is suppressed (for example, 21.5 has stem 2 and leaf 1). What do you perceive as the most prominent feature of the display?

b. Draw a histogram based on the 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.

c. Use a calculator or statistical computer package to calculate logarithms of these observations and construct a histogram. Is the logarithmic transformation satisfactory?

d. Consider transformed value 5 1

!original value and construct a histogram of the transformed data. Does it appear to resemble a normal distribution?