9 - Control of Extraneous Variables

Question 1

Define reliability? What are the two types?

Answer 1

Consistency of a research study

External and internal

Question 2

Define external reliability. How can it be assessed?

Answer 2

Wether a test is consistent over time.

Test-retest method can be used to assess it. Study is conducted more than once and if similar results each time then it is reliable.

Question 3

Define internal reliability. How can it be assessed?

Answer 3

Wether a test is consistent within itself.

Split-half technique assesses the internal reliability of questionnaires. Questionnaire split in half and if participants score similarly on both halves then the questions measure the same thing and has reliability.

Question 4

Define validity. What are the two types?

Answer 4

Wether a study is measuring what it intends to measure.

Two types : external and internal

Question 5

Define external validity and give examples of it

Answer 5

The extent to which the findings of a study can be generalised to other settings.

Examples:

Ecological validity
Participant validity ( results can be generalised to target population )
Historical validity ( can be generalised to people today )

Question 6

Define internal validity. How do you ensure a study has it?

Answer 6

When the outcome of the study is a direct result of manipulation of the independent variable and has not been affected by extraneous variables.

Controlling extraneous variables ensures a study has internal validity.

Question 7

What are the three types of extraneous variables?

Answer 7

Participant variables
Situational variables
Experimenter variables

Question 8

Define participant variables. How is this avoided?

Answer 8

Characteristics of the participants which may affect the DV such as intelligence, age, gender, personality etc.

Matched pairs and repeated measures can help avoid this.
Random allocation of participants to conditions ensures that groups are not biased.

Question 9

Define situational variables. How is this reduced / avoided?

Answer 9

Factors in the environment where the experiment is conducted that could affect the DV such as temperature, time of day, lighting, noise etc.

Standardisation reduces this, which is when you make sure all the conditions, materials and instructions are the same for all participants.

Question 10

Define experimenter variables. How is this reduced / avoided?

Answer 10

Factors to do with the experimenter which can affect the DV such as their personality, appearance and conduct.

Standardised instructions ensures that the experimenter acts in a similar way with all participants.

Question 11

Define demand characteristics

Answer 11

When the participant guesses a study’s purpose and what is expected of them.

They then may :
try to please the experimenter by giving the right results
try to annoy them by giving the wrong results ( screw you effect )
act unnaturally out of nervousness
act unnaturally out of social desirability

Question 12

How can demand characteristics be overcome?

Answer 12

Single blind technique

This is where the participants do not know what the hypothesis is or what condition they are in.

This is difficult to accomplish in repeated measures.

Question 13

What are investigator effects?

Answer 13

When investigators may inadvertently influence the results of their research. Certain physical characteristics of the investigator such as age, gender and ethnicity can influence the behaviour of participants.

If they know the hypothesis they may inadvertently be biased in their interpretation of the results.

Observer bias and interviewer effects are a type of investigator effects.

Question 14

How can investigator effects be reduced?

Answer 14

Double blind technique

This when neither the participants nor the investigator know the hypothesis or what condition the participant is in.