Lecture 2

Question 1

Why is a good experimental design important?

Answer 1

As behaviour and cognition follow certain predictable patterns, or be able to infer associations and causality we require a good experimental design

Question 2

Why is figuring out psychological principles of human behaviour and cognition so difficult?

Answer 2

Some reasons are exceptions, variance, researchers are human and pattern seekers, observing affects the observed, behaviour and cognition are multiply determined

Question 3

Noise

Answer 3

Noise - extraneous variables in an experiment that influences the dependant variable but that is even,y distributed across the experimental conditions.
Noise doesn’t threaten validity but it decreases the ability to detect an effect statistically

Question 4

How do you work out effect?

Answer 4

Effect = signal+noise divided by noise

Question 5

How do you minimise noise?

Answer 5

Good research design

Question 6

What is reliability?

Answer 6

Is the measure consistent/stable?

Actual measure = hypothetical true score + measurement error

Question 7

What is validity?

Answer 7

Does the measure or study truly asses the variable interest?

Internally valid vs externally valid

Question 8

What are confounds?

Answer 8

Nuisance variables that vary systematically with the IV and influence the DV in consistent ways
Threatens internal validity

Question 9

What are the three types of confounds?

Answer 9

Person
Operational
Procedural

Question 10

What is a person confound?

Answer 10

When individual differences covariant with the independent variable
Threatens internal validity
Can randomly assign individuals, can try and use matching e.g. ensure same amount of males and females in each group

Question 11

What are operational confounds?

Answer 11

When a measure designed to asses a particular construct inadvertently measures something else as well
Threatens construct validity
One option is to refine the operational definition

Question 12

What are procedural confounds?

Answer 12

The researcher manipulates one thing (IV) but inadvertently another thing covaries with it
Threatens internal validity
One option is to repeat study while controlling this variable

Question 13

What are within subject confounds?

Answer 13

Carryover effects:

Practice, fatigue, order, priming, interference, framing

Question 14

What threats are there to internal validity in studies extending over time?

Answer 14

History - other things may have happened in the world
Maturation - natural changes to the subject, not just age, e.g. symptom fluctuation
Instrumentation - the measuring instrument has changed or is not identical
Attrition (subject mortality)
Regression to mean - tendency for people who receive very hi or low scores to score closer to the mean in subsequent measure - researchers consistently underestimate this (measurement = true score + noise)

Question 15

How do you minimise confounds?

Answer 15

Random assignment,
control group: random assignment matching, undergo the same except when using placebo
Placebo effect sham operation

Question 16

What are common approaches to minimising confounds?

Answer 16

Double blind placebo controlled (as opposed to open label)
Randomised controlled trials
Counterbalancing - complete (n!) or partial - Latin square, random, reverse (abccba)
Control conditions
Pre test measurements
Pilot studies

Question 17

What is artefact?

Answer 17

When a variable is held constant in a study but influences the relation between the independent and dependent variables.
This is a threat to external validity. It can be reduced through random selection and maximising experimental realism.

Question 18

What is experimenter bias?

Answer 18

Inadvertently doing something leading subjects to behave in ways that confirm (or disconfirm) the hypothesis e.g treating participants differently or selective observations

Reduce it using double blind procedures and strict protocol adherence

Question 19

What are subject biases?

Answer 19

Hawthorne effect
Participant reaction
Evaluation apprehension
Good subject effects

Question 20

How do you reduce subject biases?

Answer 20

Single blind procedures
Manipulation checks e.g. mood ratings following mood induction
Reducing demand characteristics - disguise the hypothesis from subjects
Structured debriefing e.g. so what do you think the study was looking for?
Providing a cover story
Guarantee anonymity
Use of unobtrusive or indirect measurements

Question 21

What is selection/subject selection bias?

Answer 21

The relationships between certain subjects and environmental variables that may arise when people with different biological, behavioural and psychological characteristics select different types of environments/situations

Question 22

What are sampling biases?

Answer 22

When the sample does not correctly represent the research population (often critical for survey research)

Question 23

What are ceiling and floor effects?

Answer 23

Insufficient variation in performance because the task is too easy or difficult
E.g. everyone circles 1 on likert scale or scores 95% and above on a test

Question 24

Golden rules for the aspiring researcher

Answer 24

Design best study you can
Pay attention to detail
Document everything
Be able to justify everything