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 CJ 301

Assignment #6

CONFIDENCE INTERVAL – CI

You must read and use the CI module while working on this assignment – Confidence Interval module. (Also, use the Z score and the T score table, Be careful!).

You can consult with your classmates but I will not accept 2 matching assignments. This action will result in 0 on both assignments!!

 Due date: March 1 – Sunday (by midnight)

 *20 points total

1. A study was conducted in 2010 examining the relationship between alcohol and spousal violence using a sample of male parolees (n = 18).  One of the first objectives of the study was to assess the extent of alcohol problems in the parolees’ lives.  To do this, parolees were asked 20 questions relating to alcohol dependence ( e.g., “Do friends or family members tell you that you drink too much?” “Have you wanted to stop drinking but couldn’t?”).  Based on these questions, these investigators constructed an index measured at the interval/ratio level to quantify the extent of drinking problems in each parolee’s life.  For the sample, the mean number of alcohol problems obtained from this index 7.09 problems with a sample standard deviation of 6.11 problems.  Construct a 95% confidence interval around the estimated mean number of alcohol problems obtained from this sample.                       (5 points)

    

    

    

    

    

    

    

    

    

    

    

    

2. Construct an 80% confidence interval around the estimated mean number of alcohol problems obtained from this sample (question 1).                    (5 points)

    

    

    

    

    

    

    

3. A hypothetical study concerned with estimating the amount of marijuana use per year among a teenage population obtained a sample of 110 high (n=110) school students.  With the following sample statistics, construct a 75% confidence interval around the mean number of times this sample used marijuana in a given 1-year period:

         (5 points)

    

   Mean = 6.5 times per year                       sd= 4.2 times per year                        n = 110

    

    

    

    

    

    

   4.  Using the data in question #3, construct a 90% confidence interval around the mean number of times marijuana was used.                                                          (5 points)