Comparing Means with a Control (3 of 4)

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The critical value of t_d depends on the number of means in the experiment. Critical values can be obtained from a table of Dunnett's test.

In a hypothetical experiment described earlier, the effectiveness of Aspirin, Tylenol, and a Placebo were measured. The data are reproduced below.

Aspirin      Tylenol    Placebo
   3            2          2
   5            2          1
   3            4          3
   5            4          2

The analysis of variance summary table is shown below:

Source   df    Ssq    Ms     F    p
 Groups   2    8.0  4.00   3.60 0.071
 Error    9   10.0  1.111
Total    11   18.0  1.636