One is:(adsbygoogle = window.adsbygoogle || []).push({});

http://en.wikipedia.org/wiki/Chi-squared_distribution

where at the bottom of the page, chi-square = sum of something devided by variance.

However, here:

http://www.napce.org/documents/research-design-yount/23_chisq_4th.pdf [Broken]

where the chi-square formula is that the sum of the same thing devided by expectation value.

Which formula is right then?

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Why does Chi-square formula have two different ones?

**Physics Forums | Science Articles, Homework Help, Discussion**