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Thirty years ago, the Bureau of Justice Statistics reported in Profile of Jail Inmates that the median educational attainment of jail inmates was 10.2 years. Ten current inmates are randomly selected and found to have the following educational attainments, in years.
Assume that educational attainments of current jail inmates have a symmetric, non-normal distribution. At the 10% significance level, do the data provide sufficient evidence to conclude that this year s median educational attainment has changed from what it was 30 years ago?
a. Use the t-test.
b. Use the Wilcoxon signed-rank test.
c. If this year s median educational attainment has in fact changed from what it was 30 years ago, how do you explain the discrepancy between the two tests? |
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