Extraneous differences are held constant across conditions.

Participants cannot be returned to their original state after each condition.

Demand characteristics may result from hypothesis guessing with repeated testing.

Order effects can threaten internal validity.

fatigue

selection

practice

boredom

role of the participant

price that the buyer will pay

price that the seller will accept

name of the participant

within-groups

repeated measures

pretest/posttest

posttest only

independent groups

within-groups

concurrently

as a participant variable

All participants in the 2-minute condition are tested at 8:00a.m., those in the 5-minute condition are tested at noon, and those in the 10-minute condition are tested at 4:00 p.m.

The same list is used for each condition and is randomized for each participant.

The three groups are run simultaneously in three different rooms, and the room for each condition is randomly chosen before each group arrives.

Three different experimenters administer the task and rotate which condition they are administering.

pilot studies

checking for statistical significance

manipulation checks

adding additional conditions

depth perception

number of trials

disparity from perfect alignment

eye/eyes used

construct

internal

statistical

external

elimination of practice effects

assurance of equivalence of the groups

requirement of fewer participants

more statistical power

by using a control group

by using matched-groups design

by random assignment of participants

by using a pretest/posttest design

that each participant will have a unique order of the conditions

that the order of the conditions will be randomized for each group

that each condition appears in each position within the order at least once

that all possible orders of conditions will be used

six

ten

twenty

thirty

demand characteristic

selection effect

experimenter bias

carryover effect

dependent

independent

control

confound

not existent

weak

moderate

strong

treatment

comparison

experimental

control

the percentage correct

the number of objects

the length of exposure

the number of trials

distance out of alignment of the rods

how long the participant takes to complete the experiment

improvement in performance by the participant

eye/eyes used

role of the participant

value selected for the mug

type of mug

name of the participant

the percentage correct

the number of objects

the length of exposure

the number of trials

weak

moderate

strong

This cannot be determined without knowing the number of participants.

four

eight

sixteen

twenty-four

construct

internal

statistical

external

independent groups

concurrent measures

matched-groups

within-groups