The males of stalk-eyed flies (Cyrtodiopsis dalmanni) have long eye stalks. The females
sometimes use the length of these eye stalks to choose mates. (See Example 11.2.) Is the male's
eye-stalk length affected by the quality of its diet? An experiment was carried out in which two
groups of male "stalkies" were reared on different foods (David et al. 2000). One group was fed
corn (considered a highquality food), while the other was fed cotton wool (a food of substantially
lower quality). Each male was raised singly and so represents an independent sampling unit. The
eye spans (the distance between the eyes) were recorded in millimeters. The raw data, which are
plotted as histograms at right, are as follows: Corn diet:
2.15,2.14,2.13,2.13,2.12,2.11,2.10,2.08,2.08,2.08,2.04,2.05,
2.03,2.02,2.01,2.00,1.99,1.96,1.95,1.93,1.89 Cotton diet: 2.12, 2.07, 2.01, 1.93, 1.77, 1.68, 1.64,
1.61, 1.59, 1.58, 1.56, 1.55, 1.54,1.49,1.45,1.43,1.39,1.34,1.33,1.29,1.26,1.24,1.11,1.05 These
data can be summarized as follows, where the corn-fed flies represent treatment group 1 and the
cotton-fed flies represent treatment group 2 . a. What is the best test to use for comparing the
means of the two groups? Why?
Whitlock \& Schluter, The Analysis of Biological Data, 3e 2020 W. H. Freeman and Company
Eyespan (mm) Whitlock \& Schluter, The Analysis of Biological Data, 3e 2020 W. H. Freeman
and Company.
The males of stalk-eyed flies (Cyrtodiopsis dalmanni) have long e.pdf
1. The males of stalk-eyed flies (Cyrtodiopsis dalmanni) have long eye stalks. The females
sometimes use the length of these eye stalks to choose mates. (See Example 11.2.) Is the male's
eye-stalk length affected by the quality of its diet? An experiment was carried out in which two
groups of male "stalkies" were reared on different foods (David et al. 2000). One group was fed
corn (considered a highquality food), while the other was fed cotton wool (a food of substantially
lower quality). Each male was raised singly and so represents an independent sampling unit. The
eye spans (the distance between the eyes) were recorded in millimeters. The raw data, which are
plotted as histograms at right, are as follows: Corn diet:
2.15,2.14,2.13,2.13,2.12,2.11,2.10,2.08,2.08,2.08,2.04,2.05,
2.03,2.02,2.01,2.00,1.99,1.96,1.95,1.93,1.89 Cotton diet: 2.12, 2.07, 2.01, 1.93, 1.77, 1.68, 1.64,
1.61, 1.59, 1.58, 1.56, 1.55, 1.54,1.49,1.45,1.43,1.39,1.34,1.33,1.29,1.26,1.24,1.11,1.05 These
data can be summarized as follows, where the corn-fed flies represent treatment group 1 and the
cotton-fed flies represent treatment group 2 . a. What is the best test to use for comparing the
means of the two groups? Why?
Whitlock & Schluter, The Analysis of Biological Data, 3e 2020 W. H. Freeman and Company
Eyespan (mm) Whitlock & Schluter, The Analysis of Biological Data, 3e 2020 W. H. Freeman
and Company
