experimental independent random group design/issues

Question 1

goals of scientific method

Answer 1

description: describe events and relationships between variables using nomothetic approach and quantitative analysis
prediction: correlational relationships allow prediction of behaviours/events, but do not allow inferences on causes of these relationships
explanation: understand the cause of the phenomena when 3 conditions are met: covariation, timeorder relationship, elimination of alternatives
application: apply knowledge and research to improve lives

Question 2

construct validity

frequency claims

Answer 2

how well have you measured the variable in question

Question 3

construct validity

association

Answer 3

how well have you measured each of the 2 variables in the association

Question 4

construct validity

causal claims

Answer 4

how well have you measured or manipulated the variables of the study

Question 5

statistical validity

frequency

Answer 5

how large is the margin of error

Question 6

statistical validity

association

Answer 6

how strong is the association (effect size) is it statistically significant

Question 7

statistical validity

causal claims

Answer 7

is there a difference between groups and how large is it (what is the effect size) is the difference between groups statistically significant

Question 8

internal validity

frequency

Answer 8

not relevant

Question 9

internal validity

association

Answer 9

not asserting causality, but should ask if researchers control for other variables when they analyse the relationship

Question 10

internal validity

causal claims

Answer 10

only experimental design can establish causation. was it an experiment, does it control for alternate explanations by limiting confounds and by random assignment to groups. does it avoid several internal validity threats

Question 11

external validity

frequency

Answer 11

how representative is the sample, was it a sample of the pop of interest

Question 12

external validity

association

Answer 12

how representative is the sample, to what other settings of problems might the association be generalised, to what pop settings and times can we generalise this association claim?

Question 13

external validity

causal

Answer 13

how rep is the sample, do the manipulations in the experiment generalise to other situations/settings to what pop/setting/time can we generalise causal claim

Question 14

Logic of Experimental Research

Answer 14

Manipulate an independent variable (IV) in an experiment to observe the effect on behaviour. The effect on behaviour is assessed by the dependent variable (DV)
An IV must have at least two levels/conditions
Treatment and control (or comparison)

Question 15

Identifying the IV and DV

Answer 15

IV exists as levels. The values are categorical.

Question 16

To state the IV caused the observed changes in the DV (effect)
3 conditions need to be satisfied

Answer 16

+Covariation
+Time-order relationship
+Elimination of plausible alternative causes
When the 3 conditions are met, the experiment is said to have internal validity.
+Covariation – observe a relationship between IV and DV
+Time-order relationship – manipulate an IV and then observe a subsequent difference is behaviour
+Experimental control allows researchers to make causal inference because it eliminates plausible causes
Control is the essential ingredient of experiments
Gained through (1) manipulation, (2) holding conditions constant , and (3) balancing

Question 17

Experimental Manipulation

Answer 17

Not just observing to collect data or responding to a survey to collect data
Involves exposing different people or groups of people to different experimental conditions (sometimes groups do not know which condition they are in) and comparing the outcomes of the groups
To manipulate: the researcher actively changes the condition of the different groups to test the effect/outcome from each group, and
To draw conclusions of causality

Question 18

Holding Conditions Constant

Answer 18

A control technique to avoid confoundings
Holding conditions/factors/variables constant means
they do not change (variables are the same for all groups)
they cannot possibly covary with the IV
They are held constant because they are thought to influence the behaviour we are studying , hence they are referred to as plausible alternative causes.
There is the possibility that there may be confounding factors that were not anticipated

Question 19

Balancing

Answer 19

Comparable groups in terms of individual differences, e.g., personality, intelligence, etc.
Individual differences cannot be held constant
Apply balancing technique to establish equivalent groups
Balancing = averaging individual differences across conditions. How is this achieved?
Random assignment of participants to conditions

Question 20

Assigning Group Members

Answer 20

How should the participants be assigned so that confounding variables (e.g., individual differences) are counterbalanced or distributed across the experimental conditions?
How many to assign to each group? Sample size?
A priori power analysis (e.g., using Gpower - more about this in Week 4)

Question 21

Independent Groups Design – Randomised Groups

Answer 21

1. initial sample
2. randomised assignment to one of two or more groups
3. independent variable manipulation
4. dependent variable measured

Question 22

Block Randomisation

Answer 22

A common procedure to carry out random assignment
Random order the conditions
For example: 3 conditions:
Imagery (I); Rehearsal (R), and Control (C)
Assign a number to each condition:
I = 1, R = 2 and C = 3
Use a random number table (SZZ 9th ed. Pg 443/10th ed. Pg 438) or randomise the numbers in excel
Using random number table: 1-5-6-6-4-1-0-4-9-3-2-0-4-9-3-2-8-3-9-1-9-1-1-3-2-1-9-9-9-5-9-5-1-6-8-1-6-5-2-2-7-1-9-5-4-8-2-2-3-4-6-7-5-1-2-2-9-2-3
If we want to have 4 participants for each condition, we would need to have 4 blocks consisting of the 3 randomised conditions.
You have Participant A, F, G, and K for Imagery.
You have Participant C, E, J, and L for Rehearsal.
You have Participant B, D, H, and M for Control

Question 23

Internal Validity

Answer 23

The degree to which a researcher draws accurate conclusions about the effects of the IV = when an experiment is internally valid, the researcher can confidently conclude that differences were due to the IV.
Nothing differ systematically other than the IV, i.e. no confounding has occurred. Confounding is a fatal flaw

Question 24

Threats to Internal Validity

Answer 24

The Pepsi Challenge in 1975:
A taste test in which people were asked to taste two cola beverages and indicate which they preferred. As it was originally designed, glasses of Pepsi were marked with a letter ‘M’ and glasses of Coca-Cola were marked with a ‘Q’. People seemed to prefer Pepsi to Coca-Cola in these tests, but a confound was present. What was it?
Intact Groups (not individuals), e.g., psychology students
Subject Loss or Attrition
Mechanical subject loss
Selective subject loss (a more serious matter)
Subjects are lost differentially across the conditions of the experiment
When some characteristic of the subject is responsible for the loss
When this subject characteristic is related to the DV used to assess the outcome of the study

Placebo Control and Double-Blind Experiments (not common in psychology

Question 25

External Validity

Answer 25

The degree to which the results obtained in one study can be replicated or generalised to other samples, research settings, and procedures
Refers to the generalisability of the results
Internal validity and external validity are inversely related to some extent
The more tightly the experimenter controls the experimental setting, the more internally valid the results but the lower the external validity
Is the goal of experimental research to generalise to the real world