Tracy works in a drugstore photodeveloping department Over t
Tracy works in a drugstore photo-developing department. Over time, Tracy felt that the number of rolls of film brought in for development varied among the days of the week. Were the weekends having an effect one way or another? Tracy decided to keep a daily record of the number of rolls of film dropped off for development for 4 weeks. Her results are in the following table.
Using a one-way ANOVA, test the claim that the mean number of rolls of film dropped off is not the same for all 7 days of the week. Use a level of significance of .05.
(a) Find the test statistic. (Give your answer correct to two decimal places.)
(b) Find the critical value. (Give your answer correct to two decimal places.)
(c) State the appropriate conclusion.
| M | Tu | W | Th | F | Sa | Su |
| 33 | 30 | 42 | 24 | 32 | 20 | 17 |
| 28 | 24 | 39 | 24 | 20 | 38 | 14 |
| 47 | 28 | 14 | 23 | 22 | 9 | 13 |
| 37 | 35 | 43 | 21 | 25 | 16 | 17 |
Solution
First find mean and std deviation for each day.
Now prepare anova table:
As p value = 0.016 <0.05
reject null hypothesis.
There is significant difference for all days.
| M | Tu | W | Th | F | Sa | Sun | |
| 33 | 30 | 42 | 24 | 32 | 20 | 17 | |
| 28 | 24 | 39 | 24 | 20 | 38 | 14 | |
| 47 | 28 | 14 | 23 | 22 | 9 | 13 | |
| 37 | 35 | 43 | 21 | 25 | 16 | 17 | |
| Mean | 36.25 | 29.25 | 34.5 | 23 | 24.75 | 20.75 | 15.25 |
| Std dev | 8.057088 | 4.57347424 | 13.77195 | 1.414214 | 5.251984 | 12.36595 | 2.061553 |
