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. 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 high quality 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 below, are as follows: Corn diet: 2.15, 2.14, 2.13, 2.13, 2.12, 2.11, 2.1, 2.08, 2.08, 2.08, 2.04, 2.05, 2.03, 2.02, 2.01, 2, 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 a) what is the best test to use for comparing the means of the two groups? why? b) carry out the test identified in part (a), using alpha = 0.01
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. 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 high quality 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 below, are as follows:
Corn diet: 2.15, 2.14, 2.13, 2.13, 2.12, 2.11, 2.1, 2.08, 2.08, 2.08, 2.04, 2.05, 2.03, 2.02, 2.01, 2, 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
a) what is the best test to use for comparing the means of the two groups? why?
b) carry out the test identified in part (a), using alpha = 0.01
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