Chapter 2 - Research Methods

Question 1

Between-subject vs Within-subject design?

Answer 1

• Between-subject design: participants assigned to either test (independent variable) group, or control (placebo) group
• Within-subject design: participants act as their own control group; measurement taken before and after independent variable

Question 2

What are the two characteristics of an experiment?

Answer 2

• Random selection and assignment of participants to an;

- Independent variable manipulated by researcher

Question 3

What is an independent variable?

Answer 3

A variable that an experimenter manipulates

Question 4

What is a dependent variable?

Answer 4

The variable that the experimenter measures to see whether manipulation has an effect.

ex, school grades, health, conviction rates, etc

AKA “outcome variable”

Question 5

Internal validity vs external validity

Answer 5

Internal validity: extent to which we can infer cause and effect

• Low in naturalistic, case studies, correlational design
• High in experimental design

External validity: extent to which we can generalize findings to the real-world

• Can be low in experimental design
• High in naturalistic design

Question 6

Advantages of experiment

Answer 6

• Manipulate variables
• Show cause and effect
• Conclude that any difference in DV was caused by IV

Question 7

Disadvantages/pitfalls of experiment

Answer 7

• Placebo
• Nocebo
• Hawthorne effect (reactivity)
• Rosenthall effect (experimenter expectancy=biased outcome)

Question 8

When would one use a correlational instead of an experiment?

Answer 8

• unethical (pepsi in pregnant women)

- impossible

Question 9

What is positive correlation?

Answer 9

When both variables move in the same direction (UP or DOWN)

Question 10

What is negative correlation?

Answer 10

When variables move in opposite directions

Question 11

What is the range of r values?

Answer 11

-1.0 to +1.0

Question 12

What are the strengths of some correlations?

Answer 12

(in absolute values + or -)
1 perfect
0.8 strong
0.5 moderate
0.3 weak
0 none

Question 13

Can you infer cause and effect from correlational studies (IV or DV influence each other)?

Answer 13

No. But it’s possible if the correlation is strong enough.

Question 14

Mean

Answer 14

Average (sum, divided by n). Type of central tendency (Influenced by outliers).
2, 2, 7, 2, 2, 3 = 18/6
Mean=3

Question 15

Median

Answer 15

Middle score in an ordered data set; 50th percentile. Type of central tendency.
2, 2, 7, 2, 2, 3 = 2, 2, 2, 2, 3, 7
Median=2

Question 16

Mode

Answer 16

Most frequent score in the data set. Type of central tendency.
2, 2, 7, 2, 2, 3
Mode=2

Question 17

Low variability vs high variability?

Answer 17

Low var. = values clustered around middle

High var. = values spread out toward extremes

Question 18

Range

Answer 18

Difference between lowest and highest value. A way of calculating variability.
2, 2, 7, 2, 2, 3
Range=5

Question 19

Statistical Significance

Answer 19

• Typically a calculation based on on number of values (n) and standard deviation (SD)
• ex, “95% confidence” “p < 0.05”

Question 20

Central Tendency

Answer 20

Sense of central score of data where the group tends to cluster

Question 21

Standard Deviation

Answer 21

Average distance from mean. A way of calculating variability.