23. Choosing a statistical test (A2)

Question 1

What is a statistical test?

Answer 1

Used in psychology to determine whether a significant difference or correlation exists, and consequently whether the no hypothesis should be rejected or retained.

Question 2

What are the eight statistical tests in psychology?

Answer 2

The Chi Squared test
The Sign test
Mann-Whitney test
Wilcoxon test
Spearman's Rho
Pearson's r
Related t-test
Unrelated t-test

Question 3

Which three factors determine which statistical test should be used?

Answer 3

1. Whether the data is looking for a difference or correlation
2. Whether the experimental design is related or unrelated
3. Whether the data is nominal, ordinal or interval

Question 4

What is the mnemonic to remember the 8 statistical tests in the order they are in the table?

Answer 4

Simon (sign) Cowell (Chi) Wants (Wilcoxon) More (Mann-Whitney) Singers (Spearman’s) Receiving (Related -t) Unanimous (Unrelated-t) Praise (Pearson’s)

Question 5

What are the categories on the table showing the different statistical tests?

Answer 5

Testing for; difference or association
Design; Related or Unrelated
Data; Nominal, Ordinal, Interval

Question 6

Which statistical test can be used for both tests of difference and association/correlation?

Answer 6

Chi-Squared test (takes up two columns on the top row)

Question 7

What is nominal data?

Answer 7

Data represented in the form of categories - discrete data bc an item can only appear in one category

Question 8

What is ordinal data?

Answer 8

Data that is ordered in some way but without regular intervals - often data from a sliding numerical scale - subjective so not totally reliable

Question 9

What is interval data?

Answer 9

Data from numerical scales that include units of equal, precisely defined size - more detailed and precise than ordinal which in turn is ‘better’ than nominal

Question 10

When should the Chi-Squared test be used?

Answer 10

Difference or association; both
Design; unrelated
Data; nominal

Question 11

When should the Sign test be used?

Answer 11

Difference or association; difference
Design; related
Data; nominal or better

Question 12

When should the Mann-Whitney test be used?

Answer 12

Difference or association; difference
Design; unrelated
Data; ordinal or better

Question 13

When should the Wilcoxon test be used?

Answer 13

Difference or association; difference
Design; related
Data; ordinal or better

Question 14

When should the Spearman’s rho test be used?

Answer 14

Difference or association; association
Design; n/a
Data; ordinal or better

Question 15

When should the Pearson’s r test be used?

Answer 15

Difference or association; association
Design; n/a
Data; interval

Question 16

When should the related-t test be used?

Answer 16

Difference or association; difference
Design; related
Data; interval

Question 17

When should the unrelated-t test be used?

Answer 17

Difference or association; difference
Design; unrelated
Data; interval

Question 18

What are all of the test on the bottom row of the table known as?

Answer 18

Parametric tests

Question 19

What are parametric tests?

Answer 19

Tests that are more powerful and robust than the others, they can detect significance in data sets that others cannot

Question 20

What are the criteria for data to be tested using a parametric test?

Answer 20

1. Must be interval level
2. Data must be drawn from a population that wld expect to show a normal distribution of the variable being measured
3. There shld be homogeneity of variance - the set of scores in each condition shld have a similar dispersion.

Question 21

What happens if you have data that wld usually require a test from the bottom row but it isn’t suitable for a parametric test?

Answer 21

You shift up one row in the table and use the ordinal test directly above the original test