# chi square with percentages

#### matnet

##### New Member
Hello
I have two sample with a very different size (n=42 and n=282) and I only know the percentages of the dependent variable (with 8 levels).

The difference between the two sample in each level of DV is very large (for example: in the first condition the percentages are 16% and 82% respectively).

I converted the percentages in observed frequencies (for example 16/100*42; 82/100*282; ect.). I performed a chi square 2x8 with spss and the p-value is not significant.
How it is possible that p-value is not significant if the differences between the frequencies of each condition are vary large? This is not the procedure to be followed when you only have the percentages?

#### hlsmith

##### Omega Contributor
Your approach seems fine. Can you post your final constructed 2X8 table so we can provide a better response on the rationale?

Thanks.

#### matnet

##### New Member
Can you post your final constructed 2X8 table so we can provide a better response on the rationale?

Thanks.
I posted a xlsx file with 2x8 table. Thanks.

#### hlsmith

##### Omega Contributor
Sorry, I don't open online files

What could be happening is that the test is under-powered, given the two distributions are truly different.

#### hlsmith

##### Omega Contributor
It would mean the two distributions (proportions for categories) are truly different, but you do not have enough data to make this conclusion. This would be a Type II Error, failing to reject the null hypothesis of no difference in distributions in the sample when the two distributions are truly different in the population.

#### matnet

##### New Member
thanks vary musch. Can I performe a different statistic to see if I have the same result?