Stats Flashcards
What is nominal data?
Data in the form of categories
What is ordinal data?
Ordered in some way but doesnt have to be equal intervals between each unit
e.g. rating psychology with a score of 1-10
What is interval data?
Based on equal numerical scales that have units of a precise size
e.g. how many seconds it took someone to run a race
What are the 3d’s
Difference - Is it a test if difference or correlation
Data - What type of data has been used
Design? - What type of experimental design has been used
How do you know if a study is a test of difference or correlation?
A test of difference = bar chart
correlation = scatter graph
What is the table for working out the correct statistical test
Independant Repeated correlation
groups measures
Nominal (chi-squared) (sign test) (chi squared)
Ordinal(Mann-whitney)(Wilcoxon)(SpearmansRho)
Interval(unrelated t-test)(related t-test)(Pearsons)
What is the pneumonic for remembering the table
Carrots should come mashed with swede under roast potatoes
What does probability range between
0-1
What is the p value selected in psychology?
0.05
What is a type 1 error?
Lenient
p value is too lenient so increases chance of a false positive
Wrongly accepting experimental hypothesis
What is a type 2 error
Strict
p value is too strict so increases the chances of false negatives
Wrongly accepting a null hypothesis
When would you choose a sign test
Nominal
Test of difference
Repeated measures
How do you calculate a sign test
Work out the difference between column a and column b (e.g. A-B for each row)
and record their sign for each row (positive or negative)
Add up the number of positive values and the number of negative values
Ignore all 0’s
The s vale is whichever sign is least frequent
This calculated value should be higher than the critical value at 0.05
What are the 2 types of hypothesis
1 tailed and 2 tailed
What does Spearman’s Rho produce
A correlation co-efficient
Weaker as it uses interval data
