A nationwide company specializing in preparing students for college and graduate school entrance exams, such as the SAT, ACT, GMAT, GRE and LSAT, had the objective of improving its ACT preparatory course. Two factors of interest to the company are the length of the course (a condensed 10-day period or a regular 30-day period) and the type of course delivery (traditional classroom or online). The company collected data by randomly assigning 10 clients to each of the four treatments that represent a combination of length of the course and the type of course.The results can be found in the data file act.csv. Based on the results of a two way anova with interaction effects, which of the following can you conclude?
A. Reject the null hypothesis that there are no Length of Course effects. The p-value for Length of Course = .028 < alpha = .05.
B. Reject the interaction effect and the main effect Length of Course because both are significant at alpha=.05.
C. Reject the null hypothesis that there are no interaction effects since the p-value for the Length of Course x Type of Delivery interaction is equal to 1.89 x 10 -5 < alpha = .05.
D. Reject the null hypothesis that there are no Type of Delivery effects because the p-value for Type of Delivery = .002 < alpha = .05.
Score | Type | Length |
26 | Traditional | Condensed |
27 | Traditional | Condensed |
25 | Traditional | Condensed |
21 | Traditional | Condensed |
21 | Traditional | Condensed |
27 | Online | Condensed |
29 | Online | Condensed |
30 | Online | Condensed |
24 | Online | Condensed |
30 | Online | Condensed |
18 | Traditional | Condensed |
24 | Traditional | Condensed |
19 | Traditional | Condensed |
20 | Traditional | Condensed |
18 | Traditional | Condensed |
21 | Online | Condensed |
32 | Online | Condensed |
20 | Online | Condensed |
28 | Online | Condensed |
29 | Online | Condensed |
34 | Traditional | Regular |
24 | Traditional | Regular |
35 | Traditional | Regular |
31 | Traditional | Regular |
28 | Traditional | Regular |
24 | Online | Regular |
16 | Online | Regular |
22 | Online | Regular |
20 | Online | Regular |
23 | Online | Regular |
28 | Traditional | Regular |
21 | Traditional | Regular |
23 | Traditional | Regular |
29 | Traditional | Regular |
26 | Traditional | Regular |
21 | Online | Regular |
19 | Online | Regular |
19 | Online | Regular |
24 | Online | Regular |
25 | Online | Regular |
The ANOVA table for the above problem
Analysis of Variance
Source | DF | Adj SS | Adj MS | F-Value | P-Value |
Length | 1 | 0.225 | 0.225 | 0.02 | 0.90020864 |
Type | 1 | 5.625 | 5.625 | 0.40 | 0.53175028 |
Length*Type | 1 | 342.225 | 342.225 | 24.26 | 0.00001888 |
Error | 36 | 507.900 | 14.108 | ||
Total | 39 | 855.975 |
From tha above ANOVA table we can conclude that Reject the null hypothesis that there are no interaction effects since the p-value for the Length of Course x Type of Delivery interaction is equal to 1.89 x 10 -5 < alpha = .05.
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