A study randomly assigned 200 lab rats to 20 different groups: 2 control groups and 18 treatment groups in which the rats were fed various amounts of genetically modified corn exposed to the pesticide Roundup. The researchers ran a separate hypothesis test for each group and found a significant (P-value

Question

A study randomly assigned 200 lab rats to 20 different groups: 2 control groups and 18 treatment groups in which the rats were fed various amounts of genetically modified corn exposed to the pesticide Roundup. The researchers ran a separate hypothesis test for each group and found a significant (P-value < 0.05) number of tumors for 2 treatment groups. The published findings received some criticism. Here is a quote about this study: "Critics point out that the type of rats used in this study are particularly prone to tumors. So if you divide up 200 of them into 20 groups, you are likely to get very high (statistically significant) tumor rates in some of the groups." What does this quote refer to?

Quizplus · Accepted Answer

The quote refers to the possibility that the statistically significant results are a Type I error, meaning that the observed effect (tumor rates) is due to chance rather than a true effect of the treatment. This is because the rats used in the study are known to be prone to tumors, so the high tumor rates in some groups could be purely coincidental.

A Study Randomly Assigned 200 Lab Rats to 20 Different