Question

Here is a link to a data set concerning treatment groups A and B. Before performing a t-test to determine if the two groups are different, researchers must first ascertain if the variance in the two groups is the same using an F test. Indicate whether the hypothesis below is the null or alternate hypothesis for the F test. null The variance in group A is equal to the variance in group B Calculate the F statistic for this data set and report it in the box below, rounded to two decimal places. Use the formula =(1-(f.dist(F, df1,df2,true) in Excel to calculate the P value for the F statistic, and report it in the box below. Do not use the rounded value for F when calculating the P value. Use the value in the spreadsheet that has not been rounded. Based on this p value, would you recommend using a Student's t test or a Welch's t test to determine if the two treatment groups have different means? Enter either Student's or Welch's in the box below.

57	70
66	27
65	15
40	86
64	49
11	16
34	57
61	29
26	73
45	71
30	98
43	46
64	88
19	22
14	53
14	59
11	94
34	18
68	68
39	62

Answer 1

The hypotheses are:

Enter data in excel.

By using excel function, VAR.S(data range) the variances of two groups are:

The F test statistic is:

The degrees of freedom are:

By using excel function =1-F.DIST(B25,19,19,TRUE), the p-value is 0.119.

Since p-value = 0.119 > 0.05, we fail to reject the null hypothesis and we can conclude that the variance in group A is equal to the variance in group B.

Based on this p value, you would recommend using a Student's t test to determine if the two treatment groups have different means.