Question

1. The purpose of a study by Granholm et al. (A-7) was to determine the effectiveness of an integrated outpatient dual-diagnosis treatment program for mentally ill subjects. The authors were addressing the problem of substance abuse issues among people with severe mental disorders. A retrospective chart review was performed on 50 consecutive patient referrals to the Substance Abuse/Mental Illness program at the VA San Diego Healthcare System.

   One of the outcome variables examined was the number of inpatient treatment days for psychiatric disorder during the year following the end of the program.    

    Among 18 subjects with schizophrenia, the mean number of treatment days was 4.7 with a standard deviation of 9.3.

   For 10 subjects with bipolar disorder, the mean number of psychiatric disorder treatment days was 8.8 with a standard deviation of 11.5.

We wish to construct a 95 percent confidence interval for the difference between the means of the populations represented by these two samples.

Answer 1