A(n) ____________________ is a research method in which the researcher manipulates a variable under carefully controlled conditions and measures whether any changes occur in a second variable

In twin studies the key comparison involves determining how many pairs of twins either have the same disorder or are free of the disorder; this involves the calculation of

a. discordance rates. b. concordance rates. c. shared environment rates. d. nonshared environment rates.

Measurement Validity is synonymous with Internal Validity.

a. true b. false