Question

1. A comparative psychologist conducted a study to compare learning performance for three species of Old World monkeys (4 green monkeys from Africa, 10 rhesus monkeys from India, and 6 baboons from Africa). The animals were tested individually on a delayed-response task. A raisin was hidden in one of three containers (placed on a moveable shelf) while the animal watched from its home cage. An opaque barrier was then put in front of the cage for one minute, removed, and then the shelf and containers were placed within reach of each monkey. If the monkey tipped over the correct container, it got the raisin as a reward. The number of trials it took until the monkey got 5 consecutive trials correct was the dependent variable. The researcher used all the monkeys that were available at the time of the study at the research facility, so the sample sizes were not equal. (This experiment was approved by the institution’s Animal Care and Use Committee.)

Complete the following ANOVA summary table given the information in the problem, then make a decision/conclusion, being sure to indicate your alpha level and the critical value from the appropriate table; you should also state an appropriate set of hypotheses for clarity. Was there a difference among species in performance of this learning task? (6)

SOURCE OF VARIANCE	SUM OF SQUARES	df	MEAN SQUARES	F
Between	380
Within	1020
Total	1400

Answer 1

The hypothesis being tested is:

H₀: µ₁ = µ₂ = µ₃

H_a: Not all means are equal

The ANOVA table is:

Source	SS	df	MS	F	p-value	F critical value
Between	380	2	190	3.17	0.0678	3.59
Within	1020	17	60
Total	1400	19

The level of significance is 0.05.

The test statistic is 3.17.

The critical value is 3.59.

The p-value is 0.0678.

Since the p-value (0.0678) is greater than the significance level (0.05), we fail to reject the null hypothesis.

Therefore, we cannot conclude that there is a difference among species in the performance of this learning task.

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