Questions 12 through 18 are based on the following scenario.
An ecologist wishes to compare the feeding habits of seagulls at the Atlantic coast with seagulls at the Pacific coast. He inspected 16 seagulls from the Atlantic coast (group 1) and found that the sample mean amount of daily food consumed was 98 grams with a sample standard deviation of 3 grams. He also studied 16 seagulls from the Pacific coast (group 2) and the sample mean was 96.3 grams with a sample standard deviation of 3.8 grams. Assume that in the two populations the daily consumption is normally distributed with common population variance.
12.State the appropriate null and alternative hypotheses for testing the claim that the Atlantic coast seagulls eat more on average than the Pacific coast seagulls.
13.Calculate the pooled estimate of the common population variance.
14.Calculate the observed test statistic value.
15.Give the corresponding p-value.
16.Using a significance level of α = 0.10, give your decision and state your conclusion in terms of the problem.
17.Report the effect size for this study.
18.According to Cohen’s conventions, approximately how large is this effect?
Questions 19 through 24 are based on the following scenario.
In a study of techniques used to measure lung volumes, physiological data were collected for 10 subjects. The values given below are in liters, representing the measured functional residual capacities of the 10 subjects in a sitting position and in a supine (lying) position.
Subject: 1 2 3 4 5 6 7 8 9 10
Sitting: 2.96 4.65 3.02 2.15 1.65 5.97 1.74 3.51 4.37 4.02
Supine: 1.97 4.05 2.29 1.68 1.58 5.43 1.78 2.81 3.70 3.75
The SPSS output is shown below. The differences were computed as Sitting minus Supine.
t-tests for Paired Samples
Number of 2-tail
Variable pairs Corr Sig Mean SD SE of Mean
SITTING 3.4040 1.383 .437
10 .975 .000
SUPINE 2.9040 1.283 .406
Paired Differences |
Mean SD SE of Mean | t-value df 2-tail Sig
.5000 .317 .100 | 4.99 9 .001
95% CI (.273, .727) |
- State the hypotheses for testing if the sitting measurements are significantly larger than the supine measurements, on average.
20.Give the observed test statistic value.
21.Give the corresponding p-value.
22.What assumptions do you need to make in order to do the test?
23.Report the effect size for this study.
24.According to Cohen’s conventions, approximately how large is this effect?