In: Statistics and Probability
Question 1)
Let's conduct the ANOVA analysis for Charlie's study.
Charlie is testing the mean cuteness scores of a sample of dogs by groups. The groups are pugs, other small dogs, medium dogs, and large dogs (4 groups). There are 5 ratings (cuteness scores) per breed.
The cuteness scores are:
Pugs (5 observations): 8, 9, 9, 7, 8
Other Small dogs (5 observations): 5, 4, 6, 4, 2
Medium (5 observations): 5, 6, 4, 6, 5
Large (5 observations): 6, 5, 9, 3, 4
In the next few items you will be asked to make calculations to conduct the ANOVA analysis with this data.
Part A)
The first step of conducting our analysis will be to calculate the Overall mean and the Group means. Fill in the blanks below:
Round your responses to 1 decimal place.
OVERALL MEAN | |
GROUP MEANS: | |
Pugs | |
Other small dogs | |
Medium | |
Large |
Using Charlie's data, and the means you calculated in the previous question, fill out the ANOVA table with the appropriate degrees of freedom, sum of squares, mean squares, and F-ratio.
You can use excel or R as a calculator, but you MUST calculate them by hand/manually. If you do not provide your work/code for the manual calculations in the previous "question" you will not get full credit.
Degrees of freedom should be provided as integers.
Other values should be rounded to one decimal place.
DF | SS | MS | F | |
Group | ||||
Residual |
Now, calculate the r-squared for the ANOVA analysis you just conducted above.
Express your answer as a proportion. Round your answer to TWO decimal places.
Answer :
By using Excel;
1) Function : average ()
Overall mean and the Group means for given data is ,
pugs | other small dogs | Medium | large | |
8 | 5 | 5 | 6 | |
9 | 4 | 6 | 5 | |
9 | 6 | 4 | 9 | |
7 | 4 | 6 | 3 | |
8 | 2 | 5 | 4 | |
means | 8.2 | 4.2 | 5.2 | 5.4 |
Overall mean | 5.75 |
2) For Analysis of Variance
Path : data < data analysis < anova for single factor
For ANOVA table with the appropriate degrees of freedom, sum of squares, mean squares, and F-ratio are :
Anova: Single Factor | ||||||
SUMMARY | ||||||
Groups | Count | Sum | Average | Variance | ||
pugs | 5 | 41 | 8.2 | 0.7 | ||
other small dogs | 5 | 21 | 4.2 | 2.2 | ||
Medium | 5 | 26 | 5.2 | 0.7 | ||
large | 5 | 27 | 5.4 | 5.3 | ||
ANOVA | ||||||
Source of Variation | SS | df | MS | F | P-value | F crit |
Between Groups | 44.15 | 3 | 14.71667 | 6.614232 | 0.004086 | 3.238871517 |
Within Groups | 35.6 | 16 | 2.225 | |||
Total | 79.75 | 19 |
3) r-squared for the ANOVA analysis is
= ss( between groups ) / ss (Total )
= 44.15 / 79.75
= 0.55