Posted by **Doris I** on Saturday, February 20, 2010 at 1:32pm.

18. Twenty students randomly assigned to an experimental group receive an instructional program; 30 in a control group do not. After 6 months, both groups are tested on their knowledge. The experimental group has a mean of 38 on the test (with an estimated population standard deviation of 3); the control group has a mean of 35 (with an estimated population standard deviation of 5). Using the .05 level, what should the experimenter conclude? (a) Use the steps of hypothesis testing, (b) sketch the distributions involved, and (c) explain your answer to someone who is familiar with the t test for a single sample but not with the t test for independent means.

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**Doris I**, Saturday, February 20, 2010 at 8:55pm
12. Four research participants take a test of manual dexterity (high scores mean better dexterity) and an anxiety test (high scores mean more anxiety). The scores are as follows.

Person Dexterit Anxiety

1 1 10

2 1 8

3 2 4

4 4 -2

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**PsyDAG**, Sunday, February 21, 2010 at 9:14am
18. Can you do a t test? The distributions will overlap with control group having a greater spread of scores. Consult your text for the differences between these two t tests. Having to think it through to explain it to someone else will help *you* to understand the similarities and differences.

12. What is your question? Although the n too small, it suggests that there might be a negative correlation between the two variables.

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