Many animals, including humans, tend to avoid direct eye contact and even patterns that look like eyes. Some insects, including moths, have evolved eye-spot patterns on their wings to help ward off predators, Scaife (1976) reports a study examining how eye-spot patterns affect the behavior of birds. In the study, the birds were tested in a box with two chambers and were free to move from one chamber to another. In one chamber, two large eye-spots were painted on one wall. The other chamber had plain walls. The researcher recorded the amount of time each bird spent in the plain chamber during a 60-minute session. Suppose the study produced a mean of M = 37 minutes in the plain chamber with SS = 288 for a sample of n = 9 birds. (Note: If the eye spots have no effect, then the birds should spend an average of = 30 minutes in each chamber.)
a. Is this sample sufficient to conclude that the eye-spots have a significant influence on the birds’ behavior? Use a two-tailed test with = .05.
b. Compute the estimated Cohen's d to measure the size of the treatment effect.
c. Construct the 95 confidence interval to estimate the mean amount of time spent on the plain side for the population of birds.
To state: The decision of hypothesis test performed for the given question using two-tailed test.
The data has the sample size of 9 with the population mean, sample mean, and sum of square (SS) is 30, 37 and 288.
The test hypotheses are:
Null Hypothesis is
Alternate Hypothesis is
Degrees of Freedom:
The critical value is obtained from the t-table for . So,
The standard error, s:
The estimated standard error, sm
To find: The Cohen’s d and for the given question.
To find: Make a 95% confidence interval estimate for the given question.
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