Lab 5: Effect of stress on plant growth and reproduction

Question 1

When do you use an single factor (one way) ANOVA test compared to a t-test?

Answer 1

An ANOVA test allows us to compare more than 2 groups (means), still with only one independent variable being manipulated
It calculates an F-stat which is the ratio of the variation between a group of means relative to the variation within a group of means

Question 2

What is the null hypothesis for a single factor ANOVA test?

Answer 2

There is no significant difference between any of the groups. This is rejected if AT LEAST 1 mean is different from the others

Question 3

What can and can’t an ANOVA test tell you?

Answer 3

Can tell you if you have a significant difference between groups, CANNOT tell you which groups are significantly different from which

Question 4

What is a Tukey-HSD post-hoc test?

Answer 4

A stats test that performs pairwise comparisons of the means after the ANOVA test is conducted.
HSD stands for honestly significant difference, and does the pairwise comparisons in a more robust way than doing multiple t-tests over and over

Question 5

How do you show which means are different from which in a lab report using a Tukey HSD test?

Answer 5

Means that are significantly different have different letters above their bars on a graph.