Question

In London, Ontario, investigators performed an experiment in which 409 juvenile delinquents were randomly assigned to either multisystem therapy or just probation. Of 211 as- signed to therapy, 87 had criminal conviction within 12 months. Of the 198 assigned to probation, 74 had criminal conviction within 12 months.

Obtain a 90% confidence interval for the difference in probability of criminal conviction within 12 months of the therapies.

Based on the result in part (a), which method is more effective?

For the confidence interval obtained in part (a), what is the corresponding margin of error?

Answer 1

therapy 87 0.4123 211 probation 0.3737 198 0.0386 estimated difference in proportion std error Se 0.0483 for 90 % CI value of z margin of error E-z*std error lower confidence bound- lower confidence bound- 1.645 0.0794 0.041 0.118

for above 90% CI =-0.041 ; 0.118

as interval contais 0 as probable value of proportion differnece we can not conclude that any method is better than other

margin of error =0.079