1H. Using GraphPad Prism - tests for difference with more than two samples

Question 1

what is ANOVA used for?

Answer 1

three or more groups

Question 2

what is the test statistic for ANOVA

Answer 2

the F value

Question 3

what is the equation for the F ratio

Answer 3

F ratio: variance between the treatments / variance within the treatments

Question 4

in ANOVA, what does circle diameter, arrow heads and arrow lengths represent?

Answer 4

circle diameter: variance of samples

arrow-heads: means

arrow lengths: distance between the means

Question 5

give the 4 steps for calculating total variance

Answer 5

1. pool all data from the 3 groups
2. calculate the grand mean and work out the difference of each data point from the grand mean
3. square it
4. add them up

Question 6

how do you work out the between groups variance

Answer 6

1. look at difference between the mean for each group and the grand mean
2. square differences
3. multiply by the number in the group
4. add them up

Question 7

how to work out within groups variance

Answer 7

1. take each group separately
2. calculate the mean for each group
3. work out the difference of each data point from its mean
4. square it
5. add them up

Question 8

what do you need to use after ANOVA if a p-value is significant and why?

Answer 8

need to use a post hoc test because ANOVA p-values only tell you at least one of the groups is different but it doesnt tell you which one

Question 9

if the ANOVA is parametric with one control group, what post-hoc test do you use?

Answer 9

you should use the Dunnett’s test

Question 10

if the ANOVA is parametric and comparing everything to each other, what post-hoc test do you use?

Answer 10

tukey’s test

Question 11

if the ANOVA is non-parametric, what post-hoc test do you use?

Answer 11

Dunn’s test

Question 12

A study investigated the concentration of a newly-discovered hormone in the blood of newly- born babies.

Suggest the name of a statistical test you could use to determine whether the data really is normally distributed

Answer 12

D’Agostino and Pearson or Shapiro-Wilk or Anderson-Darling or Kolmogorov-Smirnov