In: Statistics and Probability
QUESTION 1
Questions 1 through 4 refer to the following:
Irritable bowel syndrome (IBS) is a nonspecific intestinal disorder characterized by abdominal pain and irregular bowel habits. Each person in a random sample of 24 patients having periodic attacks of IBS was randomly assigned to one of three treatment groups, A, B, and C. The number of hours of relief while on therapy is recorded for each patient in the table below.
Treatment |
|||
A |
B |
C |
|
11.2 |
11.6 |
23.1 |
|
8.0 |
12.5 |
9.9 |
|
3.1 |
10.6 |
12.1 |
|
10.9 |
11.6 |
13.0 |
|
12.3 |
13.9 |
13.3 |
|
9.9 |
8.6 |
11.0 |
|
9.1 |
18.9 |
15.2 |
|
5.0 |
19.1 |
15.9 |
|
sample mean |
8.6875 |
13.35 |
14.1875 |
sample variance |
10.1698 |
14.4486 |
16.9270 |
Give the value of the analysis of variance test statistic used to test H0: μA = μB = μC.
1 points
QUESTION 2
What's the critical value if the .05 significance level is used?
1 points
QUESTION 3
What's the p-value?
1 points
QUESTION 4
What's the decision using the .05 significance level?
Reject H0 |
||
Don't Reject H0 |
||
Reject HA |
||
Don't Reject HA |
Question 1
Grand mean, = (8.6875 + 13.35 + 14.1875) / 3 = 12.075
Treatment Sum of Squares (SSTR) = where rj is the number of rows in the jth treatment
= [ 8 *(8.6875 - 12.075)2 + 8 *(13.35 - 12.075)2 + 8 *(14.1875 - 12.075)2 ]
= 140.5075
Error Sum of Squares (SSE) = (rj - 1) sample variances
= (8 - 1) * 10.1698 + (8 - 1) * 14.4486 + (8 - 1) * 16.9270
= 290.8178
Degree of freedom for treatments, dftr = Number of treatments - 1 = 3 - 1 = 2
Degree of freedom for Error, dfe = Number of observations - Number of treatments = 8 * 3 - 3 = 21
MSTR = SSTR / dftr = 140.5075 / 2 = 70.25375
MSE = SSE / dfe = 290.8178 / 21 = 13.84847
Test statistic, F = MSTR / MSE = 70.25375 / 13.84847 = 5.07
QUESTION 2
Critical value of F for the .05 significance level and df = 2, 21 is 3.47
QUESTION 3
P-value = P(F > 5.07, df = 2, 21) = 0.016
QUESTION 4
Since p-value is less than 0.05 significance level, we reject null hypothesis H0
Reject H0