Psy 520 Topic 7.docx

# C specify the approximate p value for this test

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(c) Specify the approximate p -value for this test result. The null hypothesis is retained at the 0.05 level since the calculated value of U of 35 is > critical U of 17. Retaining H 0 at 0.05 level, p value should be > 0.05. So p > 0.05. Chapter 20 question 20.6 A social psychologist wishes to test the assertion that our attitude toward other people tends to reﬂect our perception of their attitude toward us. A randomly selected member of each of 12 couples who live together is told (in private) that his or her partner has rated that person at the high end of a 0 to 100 scale of trustworthiness. The other member is told (also in private) that his or her partner has rated that person at the low end of the trustworthiness scale. Each person is then asked to estimate, in turn, the trustworthiness of his or her partner, yielding the following results. (According to the original assertion, the people in the trustworthy condition should give higher ratings than should their partners in the untrustworthy condition.) (a) Use T to test the null hypothesis at the .01 level. Statistical hypothesis: H 0 : Population distribution < Population distribution H 1 : Population distribution > Population distribution Decision Rule: We will reject the null hypothesis if the T observed is < or = to critical T of 7, given the number of non-zero difference scores n=11 at the 0.01 significance level. Positive differences, R+ = 63.5 Negative differences, R- = 2.5 R + + R - = 11 ( 11 + 1 ) 2

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TOPIC 7 EXERCISES 63.5 + 2.5 = 11 ( 11 + 1 ) 2 66 = 66 Wilcoxon T test: T = smaller R + or R - = minimum (63.5, 2.5) T = 2.5 Reject the null hypothesis at the 0.05 significance level for directional tests because observed T of 2.5 is < critical T of 7. In conclusion, people in the trustworthy condition give higher ratings than their partners in the untrustworthy condition. (b) Specify the approximate p -value for this test result Critical value of T is 14 at the 0.05 significance level. Observed T of 2.5 is < critical T of 14 at the 0.05 level. Consequently, the null hypothesis is rejected. P value < 0.05. Chapter 20 question 20.7 Does background music inﬂuence the scores of college students on a reading comprehension test? Sets of 10 randomly selected students take a reading comprehension test with rock, country, or classical music in the background. The results are as follows (higher scores reﬂect better comprehension): (a) Why might the H test be preferred to the F test for these data? There are 3 types of background music to be tested to determine if they have an influence on the scores. It appears that H will be better than F for the data needed. The underlying populations could be negatively skewed, so that is another reason to use the H test rather than F. (b) Use H to test the null hypothesis at the .05 level of significance. H 0 : population distribution Rock = population distribution Country = population distribution Classical H 1 : population distributions are not equal
TOPIC 7 EXERCISES Decision Rule: We will reject the null hypothesis if observed H is > critical H of 5.99, which appears in the cell intersected by the number of groups at the 0.05 level.

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• Fall '14
• dargon
• Statistics, Null hypothesis, Statistical hypothesis testing, Statistical power

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