If a = 0.05 and chance alone is operating, it is reasonable to expect that on the average one would make one Type I error in every 20 experiments.

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This statement is correct. When the significance level (a) is set at 0.05, it means that there is a 5% chance of rejecting the null hypothesis when it is actually true. Therefore, in the long run, if chance alone is operating, one would expect to make one Type I error (rejecting a true null hypothesis) in every 20 experiments.

If a = 005 and Chance Alone Is Operating, It Is Reasonable to Is