It has been proposed that drinking green tea on a regular basis will improve people's

memory, and that the more green tea you drink, the better your memory will become. To test whether this is true, people are randomly assigned to one of three groups, which will consume either no green tea, one cup of green tea daily, or 3 ?cups of green tea daily. After 4 ?weeks, the participants are given a memory test and the following summary statistics were obtained:

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No green tea 1 cup green tea daily 3 cups green tea daily ni 25 23 31 X-bar; 4.8 9.3 11.4 Si 1.85 2.04 2.18