Measures of Difference: The Chi-Squared Test Flashcards
Why are measures of association important?
They indicate the strength (and often direction) of the relationship between two variables.
What do t-tests measure?
The strength (and direction) of that association/relationship.
What does chi-squared measure?
Our (un)certainty about the presence of an association/relationship.
Why do we use chi-square as a measure of difference?
Determines whether observed differences in the data are statistically different from random.
When do we claim a significant difference?
If the value that results from this process is above a specific cut-off value, we reject the null hypothesis and claim there is a significant difference.
Write the formula for chi-squared.
χ² = the sum of ( (the observed frequencies - the expected frequencies)² / by the expected frequencies )
How do we calculate the Degrees of Freedom with one way chi-squares?
df = k - 1, where k is the number of categories in the frequency distribution.
How do we calculate the Degrees of Freedom with two way chi-squares?
df = (r – 1) * (c – 1)
r is the number of rows in the table
c is the number of columns
What is Cramers V test?
Statistical test that provides a measure of the strength of association that gives a value between 0 and 1 (where 0 indicates no association and 1 would indicate a ‘perfect’ association).
