Inferential Statistics Flashcards
What do inferential statistics mean
Nominal data and independent measures
Chi square
Ordinal and repeated measures
Wilcoxon T
Nominal and repeated measures
Sign test
Ordinal and independent measures
Mann Whitney U
Ordinal and correlation
Spearman’s rho
Nominal and correlation
Chi square
Interval and independent measures
Unrelated t test
Interval and repeated measures
Related t test
Interval and correlation
Pearsons r
How to do the Mann Whitney u test
1) if one condition has fewer subjects, call this condition a. If the have same subjects it does not matter.
2) Rank ALL the scores together, as if they belonged to just one group, but record it separately
3) find the sum of each. Call them Ra and RB
4) calculate Ua
( Na(Na + 1) )
Ua= NaNb + ( ——————- ) - Ra
( 2 )
5) calculate Ub
Ub= (NaNb)-Ua
6) then U will be the smaller one of Ua and Ub. Then find the critical value. U must be equal or smaller to be significant.
How to do the Wilcoxon T test
1) word out the difference between the scores in the two conditions. If some of the values are negative, then record this
2) rank the differences (ignoring whether the numbers are positive or negative when doing so). Give rank 1 to the lowest value and so on . BUT ignore values that are 0.
3) find the sum of the positive ranks and the sum of the negative ranks. The smaller of the two values is called T.
4) Find critical value. T must be equal to or smaller than the critical value to be significant
How to do spearman’s rho
1) rank the values of the first variable
2) rank the values of the second variable
3) find the difference between the ranks
4) square the figures obtained for the differences between the ranks and find the sum of the difference squared (∑d2)
5) apply the formula for rs
6(∑d2)
rs= 1 - ——————
N(N2-1)
6) rs must equal or exceed the critical value to be significant
How to do chi square
1) arrange the data in a table and work out the marginal totals.
2) calculate the expected frequencies (E) for each cell.
R x C
E= ————
T
R= row total
C= column total
T= overall total
3) then work out the equation
(O - E) 2
X2= ∑ ————
E
Then calculate the sum of it and call it X2
4) check the degrees of freedom (df) to do this you need to:
(R-1) x (C-1)
5) find the critical value. X2 has to be equal to or exceed the critical value to be significant
How to do sign test
