Critical Chi-squared value
The critical chi-squared value is the value that we compare our calculated chi-squared value to, to determine whether our data is significantly different from the expected values.
We can find it in a big table, called the chi-squared distribution table, which gives us the critical value based on two variables:
- The significance level
- The degrees of freedom of our contingency table
You need to use the column heading that corresponds to one minus your chosen significance level. For example, if you chose a significance level of 5% (0.05), you would look under the column heading for 0.95 (1 - 0.05 = 0.95).
We should now have two things:
- Our calculated chi squared value
- The critical chi-squared value from the table
If our calculated chi-squared value is greater than the critical chi-squared value, then we can say that there is significant evidence to suggest that the two variables are not independent.
flashcards
| Question | Answer |
|---|---|
| Critical chi-squared value | The value compared against the calculated chi-squared statistic to decide if data differs significantly from expected values. |
| Where do we find the critical chi-squared value? | In the chi-squared distribution table, based on the significance level and degrees of freedom of the contingency table. |
| How do you determine which column heading to use in the chi-squared table? | Use the column heading for one minus your chosen significance level. For a 5% significance level, look under 0.95 (1 - 0.05). |
| What does it mean if the calculated chi-squared value is greater than the critical chi-squared value? | There is significant evidence to suggest that the two variables are not independent. |