APEX AP Stats 4.1.7 Designs of Experiments Study Guide

Experimental Design

Choosing treatments and describing how subjects are to be assigned to treatments in this experiment.

What are the three types of experimental design?

1. completely randomized design 2. block design 3. matched pairs design

Completely Randomized Design

All subjects are randomly assigned to the various treatment and control groups.

Main Focus of Completely Randomized Design

Ensuring all subjects are randomly assigned to the various treatment groups.

Steps of Completely Randomized Designs

1. You can either randomly select participants into groups or randomly assign them to one of the two groups 2. you have the choice between ensuring an equal number of subjects or ensuring each individual is randomly assigned to the groups 3. randomly select one group to be the treatment group and the other to be the control group 4. collect data and infer if differences were caused by the treatment

Completely Randomized Comparative Design

a type of completely randomized design that compares more than one treatment

Random Group Selection

Randomly select one group to be the treatment group and the other to be the control group.

Hawthorne Effect

It would be best if the participants didn't know they were part of an experiment to prevent this effect.

Placebo Effect

It would be best if the participants didn't know what the treatment is to prevent this effect.

Example of Randomly Selecting Volunteers

Numbering the volunteers, putting the numbers on papers, and then randomly selecting half of them and putting them into a group.

Example of Randomly Assigning Volunteers

Flip a coin for each subject.

Block Design

The subjects are divided into specific groups to control lurking variables and reduce variability.

Data Measurement in Block Design

This design measures each group's data separately.

Matched Pairs Design

A special form of blocking where each block has two units/subjects.

What are the two forms of the matched pairs design?

1. units with similar characteristics are matched and assigned to different treatment conditions 2. before and after design

Before and After Design

The same individual is compared at two different times.

Before Measurement

The control in a before and after design.

After Measurement

The treatment condition in a before and after design.