Chi Squared (x^2)

Question 1

What type of data is the Chi squared used for?

Answer 1

Categorical data

Question 2

How do you calculate the expected count?

Answer 2

Multiply the row proportion (row total/ total count) by the column proportion (column total/total count) by the total count.

This will produce two score (one for each column/row).

This should be the same value for all possible outcomes per category-assuming evidence for the null

Question 3

What is the Chi-squared equation?

Answer 3

[the sum of the (observed value-expected value)^2]/[expected value]

repeat the equation [(observed value-expected value)^2]/[expected value] then add all the results together

Question 4

What is the observed value?

Answer 4

The frequency of each outcome occurring for each category

Question 5

What is meant by the degrees of freedom?

Answer 5

The number of cells that need to be defined so that you have enough data to work out the frequency of the other data values

Question 6

What is the equation for degrees of freedom?

Answer 6

(number of rows-1)x(number of columns-1)

Question 7

What are the assumptions of the chi-squared test?

Answer 7

1) the data points are independent (separate groups are used)
2) the data are described by the binomial distribution
3) For a good description of the test, at least 5 expected counts in each cell are needed

Question 8

If the number of counts is too small, what test can be used instead?

Answer 8

The Fisher’s exact test