Statistics for CJ Research Assignment - Testing Differences Between Means
1. Describe the situation when the one-tailed test is appropriate.
2. Draw the figures to demonstrate the left-side one-tailed test and the right-side one-tailed test, respectively.
3. List the requirements for testing the differences between means.
4. A sample of white-collar and blue-collar workers was surveyed concerning their opinions regarding police violence. Those who responded that they believe the police generally used excessive force are shown below.
|
White Collar
|
Blue Collar
|
|
Believe Excessive Force Used (f)
|
275
|
325
|
|
Sample Size
|
N1 = 425
|
N2 = 615
|
Follow the 6 steps to test the significance of the difference between the proportion of white collar workers and blue collar workers who believe the police use of excessive force. (α =.05; two-tailed test; Show your work step by step).
5. A well-evaluated cognitive behavioral program is administered to youth on juvenile probation to teach them how to reduce levels of aggression. Researchers are interested only in whether or not the youth improved (i.e., if their aggression was reduced) and have good reason to believe that the individual's aggression will decrease because research has found it to be effective. Therefore, use a one-tailed t test to identify whether or not levels of aggression (high numbers reflect greater aggressiveness) were reduced after the cognitive behavioral program. Before and after results are presented below:
|
Probationers
|
Aggression
|
|
Before (X1)
|
After (X2)
|
|
A
|
18
|
15
|
|
B
|
15
|
13
|
|
C
|
14
|
14
|
|
D
|
16
|
14
|
|
E
|
10
|
7
|
|
F
|
17
|
14
|
|
G
|
14
|
11
|
|
H
|
15
|
14
|
|
I
|
10
|
11
|
|
J
|
9
|
8
|
|
K
|
16
|
12
|
|
L
|
13
|
13
|
|
M
|
9
|
7
|
|
N
|
16
|
15
|
|
O
|
12
|
14
|
Test the null hypothesis that the cognitive-behavioral program has no effect on level of aggression. (Using α = .05; follow the 8 steps).