Chi-Squared Test

A test for the difference between two data sets.

Used with quadrat sampling.

Can a snail prefer one type of seaweed over another type of seaweed?

You are investigating a seashore and you have noticed that a small snail (the flat periwinkle) seems to live only on seaweeds of various kinds. You decide to investigate whether the animals prefer certain kinds of seaweed by counting numbers of animals on different species.

Hypotheses for snail preference of seaweed

Step 1:

Calculation of predicted value

Step 2:

Calculation of expected outcome

Step 3:

Calculation of (O - E) squared

Step 4:

Calculation of (O - E) squared divided by expected value

Step 5:

Calculation of chi-squared

Step 6:

Calculation of degrees of freedom

Step 7:

Using the chi-squared table

Step 7b:

Calculation of predicted value
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