In: Statistics and Probability
Between 20 and 25 violent acts are portrayed per hour on children’s TV. A study by Johnson et al (2002) looked for links between TV viewing and aggression by following the TV viewing habits of children 1-10 years old. Of these, 88 watched < 1 hr TV per day, 386 watched 1-3 hrs and 233 watched > 3 hrs. Eight years later, researchers looked to see if any of the children had records of aggressive assaults on other people. The numbers of children with aggressive assaults were 5, 87 and 67 for each TV category, respectively. The remaining children were not aggressive.
Question 1: Create a contingency table of the results from the study. Carry out an appropriate statistical test to determine whether TV viewing is associated with future violence. What is the conclusion from your test?
Question 2: Do the results of the study prove that TV watching behavior causes increased aggression in children? Why?
Chi-Square Test of independence | |||||||
Observed Frequencies | |||||||
0 | |||||||
0 | aggressive | not aggressive | Total | ||||
<1hours | 5 | 83 | 88 | ||||
1-3hours | 87 | 299 | 386 | ||||
<3hours | 67 | 166 | 233 | ||||
Total | 159 | 548 | 707 | ||||
Expected frequency of a cell = sum of row*sum of column / total sum | |||||||
Expected Frequencies | |||||||
aggressive | not aggressive | Total | |||||
<1hours | 159*88/707=19.791 | 548*88/707=68.209 | 88 | ||||
1-3hours | 159*386/707=86.809 | 548*386/707=299.191 | 386 | ||||
<3hours | 159*233/707=52.4 | 548*233/707=180.6 | 233 | ||||
Total | 159 | 548 | 707 | ||||
(fo-fe)^2/fe | |||||||
<1hours | 11.054 | 3.207 | |||||
1-3hours | 0.000 | 0.000 | |||||
<3hours | 4.0678 | 1.1802 |
Chi-Square Test Statistic,χ² = Σ(fo-fe)^2/fe
= 19.510
Level of Significance = 0.05
Number of Rows = 3
Number of Columns = 2
Degrees of Freedom=(#row - 1)(#column -1) = (3- 1 ) * ( 2- 1 )
= 2
p-Value = 0.0001 [Excel function:
=CHISQ.DIST.RT(χ²,df) ]
Decision: p-value < α , Reject Ho
so,
TV viewing is associated with future violence
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results of the study prove that TV watching behavior causes increased aggression in children
as TV viewing is associated with future violence
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