Which of the following statements concerning research methods and t-tests are accurate?

True False In an independent groups t-test, the null hypothesis is that the two population means are equal.


True False In order to make cause and effect conclusions, random assignment must be used in an experiment.


True False An independent groups t-test can not be used if the independent variable is simply observed rather than manipulated.


True False Limiting your sample to include only a certain type of person (e.g., only women or only average intelligence children), has the disadvantage of increasing variation within treatment groups.

Which of the following statements concerning research methods and t-tests are accurate?
First 3 statements are true.