In: Statistics and Probability
Based on the findings for the delivery below, determine if a post hoc test is necessary. If necessary:
condition 1 |
condition 2 |
condition 3 |
0 |
6 |
6 |
4 |
8 |
5 |
0 |
5 |
9 |
1 |
4 |
4 |
0 |
2 |
6 |
We used the excel data analysis tool pack to get the summary and one way ANOVA of the data, which is given below:
The Mean and standard deviation if the given data is as below:
Groups |
Count |
Sum |
Average |
Variance |
Standard deviation |
condition 1 |
5 |
5 |
1 |
3 |
1.73 |
condition 2 |
5 |
25 |
5 |
5 |
2.24 |
condition 3 |
5 |
30 |
6 |
3.5 |
1.87 |
We have to test
H0: all µi are same i.e. µ1= µ2= µ3
H1: all µi are not same i.e. at least one mean is significantly different than others
The ANOVA of the data is given below:
ANOVA |
||||||
Source of Variation |
SS |
df |
MS |
F |
P-value |
|
Between Groups |
70 |
2 |
35 |
9.13 |
0.0039 |
|
Within Groups |
46 |
12 |
3.83 |
|||
Total |
116 |
14 |
We have the p-value=0.0039 which is less than 0.05 and it indicates that we have strong evidence against H0 to reject it so we reject the null hypothesis and conclude that mean is significantly different than others.
We have a significant ANOVA (rejected H0) so we will proceed for Tukey’s HSD post hoc test
We have q(0.95,3,12)= 3.772929
EMS = 3.83
r=5
The 95% Tukey’s confidence interval for mean difference in condition 1 and condition 2 can be given as below:
Lowe limit= 0.696
Upper limit= 7.304
Above confidence interval does not include the value 0 which indicates that there is significant mean difference between condition 1 and condition 2.
The 95% Tukey’s confidence interval for mean difference in condition 1 and condition 3 can be given as below:
Lowe limit= 1.696
Upper limit= 8.304
Above confidence interval does not include the value 0 which indicates that there is significant mean difference between condition 1 and condition 3.
The 95% Tukey’s confidence interval for mean difference in condition 2 and condition 3 can be given as below:
Lowe limit= -2.304
Upper limit= 4.304
Above confidence interval includes the value 0 which indicates that there is not significant mean difference between condition 2 and condition 3.
So finally we can conclude that condition 1 is honestly significant different than condition 2 and condition 3 while condition 2 and condition 3 are not honestly significant different.