Criminal Justice Statistics

  1. You have a sample of 267 students from criminal justice, political science, finance and accounting, and electrical and computer engineering classes.  You need to examine whether your sample is representative of the entire WCU undergraduate student population in terms of age.  You know that the average age for the WCU student population is 22.8, but you do not know the standard deviation of the population.  The average age is 21.77 in your sample, with a standard deviation of 4.039.  Make sure that you apply all steps of hypothesis testing.

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2.     2. Practice using the t-table in the Appendix.  Complete the following table by filling in the degrees of freedom, the critical value, and whether you would reject or fail to reject the null.

Sample size Level of significance Obtained t-value    (step 4) Degrees of freedom Critical t-value      (step 3) Reject or fail to reject null
15 .05 1.692 Â Â Â
237 .01 -2.021 Â Â Â
41 .05 1.723 Â Â Â
101 .01 2.621 Â Â Â
27 .05 -2.754 Â Â Â

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2a.

2b.

2c.

2d.

2e.

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3.     3. You now want to see if your sample is representative of the population in terms of race.  Can you use the single sample t-test?  Why or why not?

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