psych209 LO10

treatment group/condition

participants in an experiment who are exposed to the level of the independent variable that involves a medication, therapy, or intervention

random assignment

chance method (flipping a coin) to assign participants into different experimental groups

comparison group

group in an experiment whose levels on the independent variable differ from those of the treatment group in some intended way

dependent variable

variable thats measured

selection effect

threat to internal validity in independent-groups design when participants at one level are systematically different from those at the other level

matched groups

experimental design technique where participants who are similar on some measured variable are grouped into sets; the members of each matched set are then randomly assigned to different experimental conditions

independent group design / between groups-subjects

participants only exposed to one level of the independent variable

Posttest-only design

experiment using an independent-groups design in which participants are tested on the dependent variable only once

pretest/posttest design

independent groups design where participants are tested on the key dependent variable twice: once before and once after exposure to the IV

within-groups design

experimental design where each participant is presented with all levels of the independent variable

repeated-measures design

experiment using within-groups design where participants respond to a dependent variable more than once, after exposure to each level of the independent variable

concurrent measures design

experiment using a within-groups design where participants are exposed to all the levels of an independent variable at roughly the same time, and a single attitudinal or behavioral preference is the dependent variable

what is needed in an experiment

1 IV and 2 conditions with Random assignment where participants are randomly assigned to groups, 1 DV, Ideally control for other variables

independent variable

manipulated variable

placebo

when control conditions receive a “blank” version of the treatment

control

constants