Chi Squared Flashcards
What does chi squared test?
The null hypothesis. It does this by testing whether the observed frequency of characteristics fits the frequency predicted.
What does the null hypothesis assume?
There is no relationship between 2 variables.
How big should the minimum sample be when using chi squared?
20.
What type of data must be used for the chi squared test?
Explain what this type of data is.
Discrete.
This data is a set value. It cannot be made anymore specific, by using decimal points for example. Eg: 5 people, as you can’t have 5.5 people.
What is chi squared usually used for when comparing?
Its used for comparing experimental data with theoretical data.
Give the formula (in symbols) for chi squared.
(O - E)^2
Sum of —————-
[E]
What do the symbols in the chi squared equation mean?
O - Observed members
E - Expected numbers
What are degrees of freedom?
The number of categories, -1.
If the chi squared value is larger than the critical value of 0.5, what can we assume?
What do we do to the null hypothesis?
The results are due to chance, and therefore findings are not significant.
We accept the null hypothesis.
If the chi squared value is smaller than the critical value of 0.5, what can we assume?
What do we do to the null hypothesis?
Results are not due to chance, therefore findings are significant.
We reject the null hypothesis.
Give examples of categories that may be used when calculating degrees of freedom.
Use the examples of yellow/green and round/wrinkled peas.
For this example, how many degrees of freedom would there be?
Round, yellow
Round, green
Wrinkled, yellow
Wrinkled, green
4 categories means there are 4 degrees of freedom.
What is the critical value for chi squared?
p = 0.05
