(Table: TV and Aggressiveness) In a fictional study, a pretest-posttest design w
ID: 3158391 • Letter: #
Question
(Table: TV and Aggressiveness) In a fictional study, a pretest-posttest design was used to examine the influence of a television program on children's aggressiveness. The number of aggressive responses was measured during an observation period both before and after the television program.
(a) Determine if there is a difference in the number of aggressive behaviors in children after having viewed the television program, using a 95% confidence interval.
(b) Compute Cohen's d as a measure of effect size and interpret its meaning.
Table: TV and Aggressiveness
Participant
Before
After
1
6
9
2
4
3
3
8
11
4
9
12
5
10
14
6
2
6
7
14
13
(Table: TV and Aggressiveness) In a fictional study, a pretest-posttest design was used to examine the influence of a television program on children's aggressiveness. The number of aggressive responses was measured during an observation period both before and after the television program.
(a) Determine if there is a difference in the number of aggressive behaviors in children after having viewed the television program, using a 95% confidence interval.
(b) Compute Cohen's d as a measure of effect size and interpret its meaning.
Table: TV and Aggressiveness
Participant
Before
After
1
6
9
2
4
3
3
8
11
4
9
12
5
10
14
6
2
6
7
14
13
Explanation / Answer
A.
MeanBefore = 53/7 = 7.571
MeanAfter = 68/7 = 9.714
SDBefore = 3.99
SDAfter = 3.98
Spooled =((3.99^2 + 3.98^2)/2)^0.5 = 3.985
t = (MeanAfter - Mean Before)/Spooled
= 0.537 <t14-2,0.975
Hence we cannot reject at 95% CI that the means differ.
B.
d=(MeanBefore - MeanAfter)/Spooled
= -0.537
This reflects a medium size effect
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