Problem 96E

Motivation of drug dealers. Refer to the Applied Psychology in Criminal Justice (Sept. 2009) study of the personalitycharacteristics of convicted drug dealers, Exercise 5.15(p. 251). A random sample of 100 drug dealers had a meanWanting Recognition (WR) score of 39 points, with a standarddeviation of 6 points. The researchers also are interestedin σ2, the variation in WR scores for all convicteddrug dealers.

a. Identify the target parameter, in symbols and words.

b. Compute a 99% confidence interval for σ2.

c. What does it mean to say that the target parameter lieswithin the interval with “99% confidence”?

d. What assumption about the data must be satisfied in order for the confidence interval to be valid?

e. To obtain a practical interpretation of the interval, part b, explain why a confidence interval for the standard deviation, σ, is desired.

f. Use the results, part b, to compute a 99% confidence interval for σ . Give a practical interpretation of the interval.

Motivation of drug dealers. Refer to the Applied Psychology in Criminal Justice (Sept. 2009) study of the personality characteristics of drug dealers. Recall that each in a sample of 100 convicted drug dealers was scored on the Wanting Recognition (WR) Scale, which provides a quantitative measure of a person’s level of need for approval and sensitivity to social situations. (Higher scores indicate a greater need for approval.) The sample of drug dealers had a mean WR score of 39, with a standard deviation of 6. Use this information to find an interval estimate of the mean WR score for all convicted drug dealers. Use a confidence coefficient of 99%. Interpret the result.

Motivation of drug dealers. Researchers at Georgia State University investigated the personality characteristics of drug dealers in order to shed light on their motivation for participating in the illegal drug market (Applied Psychology in Criminal Justice , Sept. 2009). The sample consisted of 100 convicted drug dealers who attended a court-mandated counseling program. Each dealer was scored on the Wanting Recognition (WR) Scale, which provides a quantitative measure of a person’s level of need for approval and sensitivity to social situations. (Higher scores indicate a greater need for approval.) The sample of drug dealers had a mean WR score of 39, with a standard deviation of 6. Assume the distribution of WR scores for drug dealers is mound shaped and symmetric.

a. Give a range of WR scores that will contain about 95% of the scores in the drug dealer sample.

b. What proportion of the drug dealers will have WR scores above 51?

c. Give a range of WR sores that will contain nearly all the scores in the drug dealer sample.

Solution

Step 1 of 6

a) We have to identify the target parameters

Here the parameter is

And the variation in WR scores for all convicted drug dealers