# Statistical tests for A2 biology

unit 6 exam

HideShow resource information

## Chi squared test

• Use when the measurements relate to sample size in different categories.
• Produce a null hypothesis: There's no difference between the expected and observed results."
• Calculate the value of chi and look at the tables.
• The degrees of freedom are one less than the number of categories.
• If the value of chi is greater than the critical value we reject the null hypothesis and say there IS a significant difference between the observed and expected.
1 of 4

## Spearman's rank correlation

• Null hypothesis: there's no association between the two variables.
• Calculate the Rs.
• Look up on table the number of measurements and the critical values for each one
• If your Rs is greater than the critical value you reject the null hypothesis.
2 of 4

## Standard error

• To find if there's difference between two means.
• Null hypothesis: no difference between the no. of seeds in the dark than the ones at the sun.
• Calculate standard error.
• 95% confidence are 1.96+ mean and mean-1.96.
• If these values don't overlap, there's a significant difference between the 2 variables. (Plot a whisker!!)
• If they overlap we accept the null hypothesis.
3 of 4

## T-test

• Significant difference between two means.
• Null hypothesis: There's no difference between the two variables.
• Calculate t.
• Degrees of freedom are both sample sizes -2.
• Look up the degrees and critical values.
• If t greater than critical, the null hypothesis is rejected.
4 of 4

Report

Report

cool, what about the Man whitney U test? that would be fab! thanks!

Report

Brilliant Thanks!

Report

this is so good its bad

Report

Thank you

## Similar Biology resources:

See all Biology resources »