1.An independent-groupsttest

Group of answer choices

compares sample means for two related groups.

compares sample means for two unrelated groups.

compares standard deviations for two unrelated group.

compares sample means for three or more unrelated groups.

2.When subjects are lost differentially from the experimental and control groups, any observed effect may be due to

Group of answer choices

mortality.

instrumentation.

diffusion of treatment.

history.