ASSIGNMENT PROBLEMS 8 The males of stalkeyed flies co manni

ASSIGNMENT PROBLEMS 8. The males of stalk-eyed flies (co manni have long eye stalks. The females sometimes use the length of these eye saalks to choose males, csee Example 11.2. Is the male\'s eye-stalk length affected by the quality of diet? An experiment was carried out in which groups of male \"stalkies\" 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 (the 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. 4, 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, I.89. Cotton diet: 2.12. 2.07, 2.01. 1.93. 1.77, 1.68, 1.64, 1.61. 1.59, 58, 1.56, 1.55, 1.54, 1.49. 1.45, 1.43, 1.39, 1.34. 1.33, 29, 1.26. 1.24. 1.11. I.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. Mean Variance Sample (mm) (mm) size, n Corn diet (group 1) 2.05 0.00558 21 Cotton diet (group 2) 1.54 0.0812 24 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 0,01 Corn de m Cotton diet 1.5 Eyespan (mm)

Solution

Here sample sizes for both are less than 30. Hence z test cannot be used.

t test can be used with df = 21-1 =20

Comparison of two means using t test.

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Set up null and alternate as

H0: mu1 = mu2

Ha: mu1 not equals mu2

Two sided test

mu1-mu2 = 0.51

std error = 1.8947

z statistic = 0.269

p value = 0.788

As p value > 0.01, accept null hypothesis

The difference between two means is not statstically significant.