Answer to Question 1
A
Answer to Question 2
D
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The history threat is the occurrence of events concurrent with the independent variable that can affect the outcome. The maturation threat arises from processes occurring as a result of time (e.g., growth, fatigue) rather than the independent variable. The selection threat reflects biases stemming from preexisting differences between groups. RCTs have a clear superiority for testing causal hypotheses. Internal validity is the extent to which it can be inferred that the independent variable is truly causing the outcome.
Four hypotheses on how populations might relate to one another along an environmental gradient.
Some organisms used as models in genetic research
Adapoids and omomyoids had longer snouts and are the first “true” primates.
A recruiting poster for the “True Sons of Freedom” encouraged African Americans to enlist. In fact,
Different ways to test hypotheses
Research Methods: A Process of Inquiry