CJ About half of the police offi cers in Shinbone, Kansas, have completed a special course in investigative procedures. Has the course increased their effi ciency in clearing crimes by arrest? The proportions of cases cleared by arrest for samples of trained and untrained offi cers are reported below.

Sample 1

(Trained)

Sample 2

(Untrained)

P s 1 = 0.47 P s 2 = 0.43 N1 = 157 N2 = 113