Research Methods 2

What is experimental research?

Experimental research is a controlled study where researchers manipulate an independent variable (IV) to see how it affects a dependent variable (DV).

Simple idea:
Researchers change one thing and then measure what happens because of that change.

What is an Independent Variable (IV)?

The independent variable is the variable that the researcher manipulates or changes.

• Think of it as the cause

• It comes before the dependent variable is measured

What is a Dependent Variable (DV)?

The dependent variable is the variable that researchers measure after manipulating the IV.

• Think of it as the effect

• It may change depending on what happens to the IV

What is the basic relationship between the IV and DV?

Independent Variable → Dependent Variable
Manipulated → Measured
Cause → Effect

What is an experimental group?

The experimental group is the group that receives the manipulation of the independent variable.

What is a control group?

The control group is the group that does not receive the manipulation.

It gives researchers something to compare the experimental group to.

What is a placebo group?

A placebo group receives an inactive/inert pill that looks like the actual medication.

The pill resembles the medication but does not contain the active treatment.

What is the difference between the experimental group and control group?

• Experimental group: receives the manipulation

• Control group: does not receive the manipulation

The major difference between them should be the independent variable.

What is the difference between a control group and a placebo group?

• A control group does not receive the manipulation.

• A placebo group receives something that looks like the treatment but is inactive.

What does it mean when researchers say experiments can establish causality?

It means experiments can help researchers determine whether changing one variable actually causes a change in another variable.

In an experiment:

IV → DV
Cause → Effect

What are the two major problems experiments help address when establishing causality?

1. Reverse causality problem

2. Third variable problem

What is the reverse causality problem?

The reverse causality problem is uncertainty about which variable caused which.

Experiments help deal with this because researchers manipulate the IV first and then measure the DV.

So the order is clear:

Manipulate IV → Measure DV

How do experiments help eliminate the reverse causality problem?

The researcher manipulates the independent variable before measuring the dependent variable.

This helps establish which variable came first.

What is the third variable problem according to this lecture?

It is the problem that some other variable could be responsible for the observed effect instead of the variable researchers are interested in.

How do experiments help with the third variable problem?

In a well-controlled experiment, the groups should differ mainly because of the manipulation of the IV.

This helps researchers connect changes in the DV to the IV rather than another variable.

What are extraneous variables?

Extraneous variables are variables that could affect the dependent variable or the person being studied.

These variables can interfere with the experiment.

What are the main extraneous variables discussed in the lecture?

• Demand characteristics

• Experimenter bias

• Participant variables

What are demand characteristics?

Demand characteristics are aspects of a study that give away the purpose of the study and cause participants to change their responses.

Simple idea:
The participant figures out what the researcher is studying and starts behaving differently.

Why are demand characteristics a problem?

Participants' behavior may be affected by what they think the researcher expects, instead of naturally responding to the experiment.

That could affect the dependent variable.

What is experimenter bias?

Experimenter bias occurs when the experimenter subconsciously changes their behavior in a way that encourages the result they expect or want.

Is experimenter bias necessarily intentional?

No. The lecture specifically describes experimenter bias as happening subconsciously.

What are participant variables?

Participant variables are characteristics of participants that could affect how they respond during an experiment.

Why are participant variables a problem?

Differences between participants could affect the DV, making it harder to know whether the independent variable actually caused the result.

What are the two major methods discussed for avoiding confounds?

• Double-blind studies

• Random assignment

What is a double-blind study?

A double-blind study is one where both the participant and experimenter are unaware of the condition the participant is in.

Who does not know the condition in a double-blind study?

Both:

• The participant

• The experimenter

What problem does a double-blind study help eliminate?

It helps eliminate potential demand characteristics.

Because participants and experimenters do not know the condition, their knowledge is less likely to influence behavior.

What is random assignment?

Random assignment means participants are randomly assigned to different experimental conditions.

What problem does random assignment help eliminate?

Random assignment helps eliminate problems associated with participant variables.

Why does random assignment help with participant variables?

Because participants are placed into conditions randomly rather than being purposely placed based on their characteristics.

The lecture identifies random assignment as the method used to reduce problems caused by participant variables.

Double-blind studies are mainly used to control what?

Demand characteristics.

Double-blind → Demand characteristics

Random assignment is mainly used to control what?

Participant variables.

Random assignment → Participant variables