Solving a Chi-Squared Test Divide by Zero Error

[Moose352]

What should I do when the expected value for a chi squared test is zero, so when I try to calculate the test statistic, i get a divide by zero?

 

[Moonbear]

The chi-squared test isn't very accurate when expected frequencies are less than 5 (and definitely not if they are 0). In some cases, you can instead use a Fisher's Exact Probability Test (if you have a 2x2 contingency table and small expected frequencies...I think less than 10). I don't have the formula for that handy though. If that doesn't work for your data, I'm not sure what other alternatives there are.

 

[tacman]

When the expected value for a chi squared test is zero, it means that there is no expected relationship between the variables being tested. In this case, the chi squared test cannot be performed because it requires a non-zero expected value.

To address this issue, there are a few options you can consider:

1. Increase the sample size: One option is to increase the sample size in your study. This can help to increase the expected values and avoid a divide by zero error.

2. Use a different test: If the expected value is consistently zero, it may be worth considering a different statistical test that is more appropriate for your data. For example, if you are testing for independence between two categorical variables, you could use a different test such as Fisher's exact test.

3. Combine categories: If possible, you can combine categories in your data to create non-zero expected values. However, this should only be done if it makes logical sense and does not alter the interpretation of your results.

4. Check your data: It is important to double check your data to ensure that there are no errors or issues that could be causing the expected value to be zero. This could include missing data or incorrect data entry.

In any case, it is important to carefully consider the implications of a zero expected value and how it may affect the interpretation of your results. Consulting with a statistician or experienced researcher may also be helpful in finding a suitable solution for your specific situation.