Chapter 18

A double-blind experiment is one in which

neither the researcher nor the participants know which participants receive the experimental treatment

A baseline in single subject research

establishes initial rates of behavior before an intervention

Interviewers may become more skilled with practice, which could cause differences between the results of participants interviewed early in the study and those of participants interviewed later. This threat to internal validity is known as

instrumentation

The internal validity of an experimental design is concerned with what question?

Did the independent variable really produce a change in the dependent variable?

In a research study in which the treatment involved quite intense physical training, 40% of the participants in the treatment group dropped out as compared with 5% of the control group. This threat to internal validity is called

experimental mortality

"To what populations, settings, treatment variables, and measurement variables can this effect be generalized?" might most appropriately be asked in relation to

external validity

It is reasonable to expect volunteer participants to be similar in nature to

other volunteers from similar populations

A researcher finds that the control group performs above its usual performance when compared with the experimental group. This effect is named the

Avis effect

Individuals performing well merely because they are being observed (and not necessarily because of any effect of treatment) are considered to be under the influence of the

Hawthorne effect

The one characteristic of true experimental designs that preexperimental and quasi-experimental designs do not have is

random assignment to groups