Suppose you test the effects of a drug on rats' learning by giving them 0, 10, 20, or 30 milligrams of the drug. This experiment has ____ independent variable(s) and ____ levels.

What is the percentage rank of z = 1.28?

Even a very small mean difference can be statistically significant if:

Group of answer choices

the sample size is big and the error variance is small

the sample size and the error variance are both big

the sample size is small and the error variance is big

the sample size and the error variance are both small

Suppose you test the effects of a drug on rats' learning by giving them 0, 10, 20, or 30 milligrams of the drug. This experiment has ____ independent variable(s) and ____ levels.

Group of answer choices

1; 4

4; 1

2; 4

4; 2