Sampling and the Experiment

What is population?

The larger group to which research results are generalized

Can you test the entire population?

No

What is a sample

A subgroup of the population

What can we assume about a sample and pop

The sample represents the entire pop

Assume the whole pop will be the same as the sample

Inclusion criteria

What the target pop should have to qualify someone as a subject

What can too many criteria do

Limit the generalizability of the study

Exclusion criteria

Factors that prevent someone from being a subject

What does random sampling mean

Every person in the pop has the same chance of being chosen

What is the end goal of random sampling

The sample is representative of the pop

What is a criteria of a random assignment

Groups should be equivalent

What is sampling error

The difference between sample and population averages

What should the sampling error be due to

Chance, not intentional error or bias

Convenience sampling

Sampling based on how available/easily accessible people

What do experiments do

Determine cause and effect oft relationships between independent and dependent variables

Experimental goals

1. Relationship between independent and dependent variables

2. Is there evidence one causes the other

3. Can this be generalized to other ideas

4. Can this be generalized to others

Three essential characteristics of experiments

1. Independent variable manipulated by researcher

2. Control group

3. Randomly assigned subjects

What can sometimes be the caveat with caring true control groups

Sometimes you can’t have them due to ethical reasons

Extraneous variables

Any outside factor that could affect the dependent variables

Confounding variable

Uncontrolled extraneous variable that messes with the experiment

Lurking variables

Variable that isn’t measured in the study but can have confounding effect

Double blinding

No one knows which group os in which

Single blinding

Only the subjects are blind