Quasi-Experimental Designs

What type of data is a quasi-experimental design

both observational and experimental

Why are quasi-experimental design studies not technically/completely considered experimental

we do not truly have a control group to compare to

Why isn’t the intervention no longer considered an IV

everyone is going to receive it

What is a quasi -experimental design

similar structure to experimental designs, but lack randomization and/or comparison group 

What kind of designs can we have with a quasi

one group pretest-posttest

one way repeated measures over time

describe a one group pretest-posttest design

independent variable is time with 2 levels (pre and post) - not the intervention

What statistical analysis is used for the one group pretest-posttest design

paired t-test

describe a one wat repeated measures design over time

often used to determine long term effects

statistical analysis used for a one way repeated measured design over time

one way repeated ANOVA

What does a one group pretest-posttest design flowchart look like

What is the purpose of an interrupted time-series design

you have a few pretest values to get an average baseline for an individual (control), the intervention, and then a few posttest value to get new normal after intervention

What are the multigroup designs

nonequivalent pretest posttest control group design

nonequivalent posttest only control group design

What is involved in a nonequivalent pretest-posttest control group design

attribute variable 

intact groups/historical controls

What is a nonequivalent pretest-posttest control group design

retrospective study of 1 group and prospective of another

When are nonequivalent posttest only control group design used

when only posttests are available (MIs)

statistical analysis of nonequivalent pretest-posttest control group design

unpaired t-test, ANOVA, Mann-Whitney U, Nonparametrics, etc

Disadvantages to nonparametric tests

don’t accommodate complex clinical designs

generally not as powerful

When are nonparametric tests used

when there is nothing to compare to (no control group)

For a nonparametric test to be as powerful as a parametric, what must happen

required a vary large sample size → more resources → more money

What is the parametric test where there are 2 independent groups

unpaired t-test

What is the nonparametric test where there are 2 independent groups

Mann-Whitney U test

When ranking scores, what are the lowest scores scored as

1 (lowest rank)

What value is used as your U statistic

the smaller value

For the U statistic to be significant, what is its relationship to the critical U

less than or equal to

What happens to U if the sample is larger

U is converted into a z score

What is indicative of a larger sample size

>25

What is the IV?

RCT to study the effects of exercise program for improving venous hemodynamics in patients with chronic venous insufficiency

31 subjects randomly assigned to 2 groups

• Experimental group received physical therapy with specific exercises for calf strengthening and joint mobility

• Control group=Nothing

• BOTH groups received compression stockings

Dynamic strength, calf pump function and quality of life were assessed at baseline and after 6 months

Exercise

How many levels to the IV?

RCT to study the effects of exercise program for improving venous hemodynamics in patients with chronic venous insufficiency

31 subjects randomly assigned to 2 groups

• Experimental group received physical therapy with specific exercises for calf strengthening and joint mobility

• Control group=Nothing

• BOTH groups received compression stockings

Dynamic strength, calf pump function and quality of life were assessed at baseline and after 6 months

2 (exercise and no exercise)

How many DV?

RCT to study the effects of exercise program for improving venous hemodynamics in patients with chronic venous insufficiency

31 subjects randomly assigned to 2 groups

• Experimental group received physical therapy with specific exercises for calf strengthening and joint mobility

• Control group=Nothing

• BOTH groups received compression stockings

Dynamic strength, calf pump function and quality of life were assessed at baseline and after 6 months

3 (strength, pump function, QOL)