Statistical tests & standard deviation

Question 1

spearmans rho

Answer 1

1. rank data for both variables
2. calculate the difference (in the same direction)
3. square the differences, add up the values
4. = 1- 6(d^2) / N(N^2-1)

Question 2

mann whitney U

Answer 2

1. rank responses in order (if there’s more than one of the same score they share a score e.g 3.5)
2. calculate the U value…. i) (Ua= NaNb + Na(Na+1) / 2 - Ra)
   (Ub= NaNb + Nb(Nb+1) / 2 - Rb)
   N = no.b of p’s R= total sum of ranks
3. the lowest U value = calculated value

Question 3

standard deviation

Answer 3

1. work out the differences
2. square the differences, add them up (getting the sum of differences squared)
3. calculate mean of d^2 scores by dividing figure by n-1
4. square root answer

Question 4

binomial sign test

Answer 4

1. difference between scores ( + or - )

2. add up the + and - scores (smallest total = calculated value)

Question 5

chi squared

Answer 5

1. work out expected frequencies for each cell ( total of row x total of column ) / overall total
2. work out differences between observed & expected frequencies for each cell
3. square difference / expected value for each
4. add up all values to get the calculated
5. work out the degrees of freedom ( no.b rows -1 x no.b columns -1)

Question 6

wilcoxon signed ranks

Answer 6

1. ignore scores for p’s who scored the same in both
2. calculate differences between scores
3. rank differences (ignore + or -)
4. add up ranks for the less frequent sign (T)

Question 7

< ???

> ???

Answer 7

= less than

= more than