Lecture 12: Quasi Experimental

Question 1

what is a quasi-experimental design?

Answer 1

a research design where researchers cannot assign participants to conditions/ manipulate the independent variable; instead comparisons are made between preexisting groups or within groups before and after the quasi treatment occured

Question 2

what is a quasi-independent variable

Answer 2

the variable that participants experience for other reasons other than the researcher manipulation bc they cannot manipulate it

Question 3

in quasi experiments, there are threats to the experiments _____ _______-

Answer 3

internal validity

Question 4

the quality of a quasi experimental design depends on how many ______ to ______ ________ it successfully eliminates; designs that eliminate ________

Answer 4

threats to internal validity…

elimination of more threats to internal validity - preferable

Question 5

Pre-test posttest design–one group

Answer 5

awful- fails to eliminate most threats to internal validity

Question 6

what is the central threat to internal validity with a simple interuprted time series deisgn

Answer 6

contemporary history - develops when another event occurs at the same time as a quasi independent variable

Question 7

in a simple interrupted time series design, ___________

Answer 7

the dependent variable is measured multiple times

Question 8

one group pretest post test design study described

Answer 8

one group is test before and after the introduction of the quasi experimental IV

–> fails to eliminate threats to internal validity

Question 9

What are threats of the internal validity in one group pretest post test designs?

Answer 9

extraneous factors

regression to the mean: tendency of the scores in a data set to move or regress toward the mean of the distribution with repeated testing= random fluctuations in participants scores from one measurement to the next, thus is the change due to this or the IV?

Question 10

nonequivalent control group design

Answer 10

researcher looks for one or more groups of participants that appear to be reasonably similar to the group that received the quasi independent variable

Question 11

nonequivalent groups post test only design

whats a threat that presents itself with this form of design?

Answer 11

two preexisting groups are studied one that experienced the quasi IV one that did not

–> threat = selection bias unequal groups

Question 12

to avoid threats to internal validity it is important that researchers______ and ______

Answer 12

select groups that are as similar as possible in as many characteristics as possible

collect as much information as possible from the two groups so that any differences can be identified and potentially controlled for

Question 13

non equivalent groups pre-test post-test design

whats a threat that may occur?

Answer 13

two preexisting groups are studied one that experienced the quasi IV one that did not BUT groups are tested twice once before the study once afterwards

local history effect extraneous event happens to one experimental group but not the other

Question 14

time series design

Answer 14

quasi experimental design where participants are tested several times throughout the experiment both before and after the introduction of the IV is introduced

Question 15

simple interrupted time series design

whats the rational behind it?

Answer 15

several pretest and post test measures

examine the effects of the quasi independent variable against the backdrop of other changes that may be occurring in the DV

Question 16

what is a central threat to internal validity with simple interrupted time series design?

Answer 16

contemporary history

when an event occurs at the same time as the quasi experimental variable

Question 17

interrupted time series design with reversal

Answer 17

DV is measured then the IV is introduced then the DV is measured then the IV is removed then the DV is measured again

Question 18

control group interrupted time series design

Answer 18

perform interrupted time series analysis on the group that received the IV and on the non equivalent control group

helps rule our certain history effects

Question 19

comparative time series design

Answer 19

examines two or more variables overtime to understand how changes in one variable lead to changes in another variable

Question 20

Longitudinal designs

when are they frequently used

Answer 20

a single group of participants is studied over time

frequently used when development psychologists want to explore age related changes in a whole host of outcomes

age is the IV

Question 21

what are the three major drawbacks of longitudinal studies?

Answer 21

difficult to obtain participants who agree to be studied again and again over a long period of time

often have trouble keeping track of participants many of whom invariably move, some may die

time effort and money!!! so much of it!

Question 22

Longitudinal > cross sectional designs

Answer 22

cross sectional designs cannot distinguish between age related changes and generational effects

differences due to generation they group up in

thus longitudinal studies as they are all one generation allow researchers to examine how an individual changes with age

Question 23

cross-sequential cohort designs

Answer 23

researchers follow two or more age groups across two or more time points

this allows researchers to tease apart age and cohort effects

can explore multiple age groups in a short period of time as compared to longitudinal designs

Question 24

disadvantages to cross sequential cohort designs?

Answer 24

attrition

findings equivalent measures

Question 25

to infer a cause and effect relation three requirements need to be met: what are they

can you infer cause and effect with quasi experimental? why or why not?

Answer 25

the cause has to precede the effect

the cause and effect must covary

participants are randomly assigned to groups and any confounding variables are controlled for

you cannot infer a cause and effect relationship because random assignment and control for confounding variables cannot be met