In: Statistics and Probability
1) The following data represent the results from an independent-measures study comparing two treatment conditions.
Treatment One |
Treatment Two |
---|---|
3 | 3.1 |
4.5 | 4.5 |
4.8 | 4.5 |
4.5 | 3.9 |
6.5 | 3.9 |
4.3 | 3.8 |
3.7 | 3.4 |
Run the single-factor ANOVA for this data:
F-ratio:
p-value:
Now, run the t test on the same data:
t-statistic:
p-value:
2) Google Sheets can be used to find the critical value for an F distribution for a given significance level. For example, to find the critical value (the value above which you would reject the null hypothesis) for α=0.05 with dfbetween=3 and dfwithin=56, enter =FINV(0.05,3,56)
Enter this into Google Sheets to confirm you obtain the value 2.769.
You conduct a one-factor ANOVA with 3 groups and 10 subjects in
each group (a balanced design). Use Google Sheets to find the
critical values for α=0.1 and α=0.05 (report accurate to 3 decimal
places).
F0.1=
F0.05=
Anova: Single Factor | ||||||
SUMMARY | ||||||
Groups | Count | Sum | Average | Variance | std dev | |
A | 7 | 31.3 | 4.471 | 1 | 1 | |
B | 7 | 27.1 | 3.871 | 0 | 1 | |
#VALUE! | ||||||
ANOVA | ||||||
Source of Variation | SS | df | MS | F | P-value | F crit |
Between Groups | 1.26 | 1 | 1.26 | 1.752 | 0.210 | 4.75 |
Within Groups | 8.63 | 12 | 0.72 | |||
Total | 9.89 | 13 |
F ratio = 1.752
p value = 0.210
=================
t test
Sample #1 ----> 1
mean of sample 1, x̅1= 4.471
standard deviation of sample 1, s1 =
1.0812
size of sample 1, n1= 7
Sample #2 ----> 2
mean of sample 2, x̅2= 3.871
standard deviation of sample 2, s2 =
0.5187
size of sample 2, n2= 7
difference in sample means = x̅1-x̅2 =
4.4714 - 3.9 =
0.60
pooled std dev , Sp= √([(n1 - 1)s1² + (n2 -
1)s2²]/(n1+n2-2)) = 0.8480
std error , SE = Sp*√(1/n1+1/n2) =
0.4533
t-statistic = ((x̅1-x̅2)-µd)/SE = ( 0.6000
- 0 ) / 0.45
= 1.324
Degree of freedom, DF= n1+n2-2 =
12
p-value = 0.2102 (excel
function: =T.DIST.2T(t stat,df) )
t statistic =1.324
p value = 0.2102
2)
F(0.1) = F(0.1,2,27) = 2.511
F(0.05,2,27) = 3.354