4. A group of 40 city parks were using what was hoped to be a crime reducing strategy in effort to combat assaults. They measured assaults and treated each park with camera monitoring devices. They tested again after the treatment. The mean before treatment (pre) was = 39.2. The parks were tested six months later to ascertain if the cameras had the desired effect. The mean after treatment (post) was = 35.83 (SEdif = 1.420). The assaults were expected to decrease after a six-month period.
Answer Difference in assualts pre post
sig
Facts
N 40.00
Mean Before 39.20
Mean After 35.83
SE dif 1.420
df 39
tcrit = df 50 2.009
t obt 2.38
n2 (computed) 0.13