In: Statistics and Probability
Please solve the following problems in their entirety. That means you will calculate a) all appropriate sums of squares, b) all appropriate mean squares, c) F statistics, d) critical value, and e) η2. Additionally, you are going to f) explain what happens to the null(s), g) relate the conclusion back to the problem, and h) perform any required post hoc tests with explanations
1. There is a study where the dependent variable is movie ratings. One independent variable is sex (male, female) and genre (drama, comedy). α =0.5
Male Female
Drama 1, 2, 9 4, 3, 8
Comedy 15, 9, 12 10, 13, 4
Descriptive statistics for each factor level is as shown below
SUMMARY | male | Female | Total |
Drama | |||
Count | 3 | 3 | 6 |
Sum | 12 | 15 | 27 |
Average | 4 | 5 | 4.5 |
Variance | 19 | 7 | 10.7 |
Comedy | |||
Count | 3 | 3 | 6 |
Sum | 36 | 27 | 63 |
Average | 12 | 9 | 10.5 |
Variance | 9 | 21 | 14.7 |
Total | |||
Count | 6 | 6 | |
Sum | 48 | 42 | |
Average | 8 | 7 | |
Variance | 30.4 | 16 |
Hypothesis:
for Factor Sex
H0 : All means are equal
H1 : All means are not equal
for Factor Genere
H0 : All means are equal
H1 : All means are not equal
For Combined effect
H0 : combinedly both genere and sex does not effect response variable
H1 :combinedly both genere and sex effect response variable
ANOVA table
ANOVA | ||||||
Source of Variation | Sum of Squares | df | Mean Square | F- statistic | P-value | F critical |
Genere | 108 | 1 | 108 | 7.714286 | 0.024019 | 5.317655 |
Sex | 3 | 1 | 3 | 0.214286 | 0.65576 | 5.317655 |
Interaction | 12 | 1 | 12 | 0.857143 | 0.38162 | 5.317655 |
Error | 112 | 8 | 14 | |||
Total | 235 | 11 |
f) α =0.5
p-value for Genere is 0.02 which is less than α hence we reject null hypothesis and we conclude that there is significant effect of genere on the response variable.
p-value for Sex and Interaction are 0.655 and 0.381 respectively and are greater than α hence we fail to reject null hypothesis and we conclude that there is no significant effect of Sex and Interaction on the response variable.
g) post hoc test can only be done for genere factor since it is only effecting response variable
multiple comparison using Tukey's procedure
Tukey Pairwise Comparisons: Genere
Grouping Information Using the Tukey Method and 95% Confidence
Genere | N | Mean | Grouping | |
2 | 6 | 10.5 | A | |
1 | 6 | 4.5 | B |
Means that do not share a letter are significantly different.
Tukey Simultaneous Tests for Differences of Means
Difference of Genere Levels |
Difference of Means |
SE of Difference |
Simultaneous 95% CI |
T-Value |
Adjusted P-Value |
2 - 1 | 6.00 | 2.16 | (1.02, 10.98) | 2.78 | 0.024 |
Individual confidence level = 95.00%