Oscar is 5 years old. If he's an average child, you'd expect him to need approximately how many hours of sleep each day?

Stress-related prenatal complications are greatly reduced when mothers

A) have partners and friends who offer social support. B) take a low dose of antianxiety medication during pregnancy. C) take a folic acid supplement during pregnancy. D) are placed on bed rest during the third trimester.

When the results of a statistical test reveal a probability of chance less than .05, a good researcher

would conclude that chance is not a likely explanation for the finding, and therefore reject the ________ of the study. A) extraneous variables B) experimental hypothesis C) null hypothesis D) validity