The average number who said they noticed was 3.1. Is the estimate from the participants signifi- cantly different from the actual number? Test the null hypothesis that the true mean is u = 3.1 using a two-tailed test with a = .05. b. Is the estimate from the participants significantly higher than the actual number (µ = 3.1)? Use a one-tailed test with a = .05. %3D %3D 14. 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 utes on the plain chamber with SS = 210 for a sample 34.5 min- 190 Ch 9 lebe Sm= *andavd tAndArd e Stimated standard of n = 15 birds. (Note: If the eye spots have no effect, then the birds should spend an average of H= 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 a = .05. b. Compute the estimated Cohen's d to measure the size of the treatment effect. c. Construct the 90% confidence interval to estimate the mean amount of time spent on the plain side for the population of birds. 15. Standardized measures seem to indicate that the aver- age level of anxiety has increased gradually over the t past 50 years (Twenge, 2000). In the 1950s, the average score on the Child Manifest Anxiety Scale was u = 15.1. A sample of n 16 of today's %3D children produces a mean score of M = 23.3 with SS = 240. %3D a. Based on the sample, has there been a significant change in the average level of anxiety since the 1950s? Use a two-tailed test with a = .01. b. Make a 90% confidence interval estimate of today's population mean level of anxiety. c. Write a sentence that demonstrates how the outcome of the hypothesis test and the confidence interval would appear in a research report.