# ChiSquare is zero even though the values are not identical

I am running a Chisquare test using CHIDIST function in Excel. My observed and expected values are not identical however i get result 0 (zero). There are 75 observed values so I am using 74 freedom points. Not sure what I am doing wrong, any assistance would be appreciated.

The description of the CHIDIST Excel function says:
Returns the right-tailed probability of the chi-squared distribution. The $$\chi^2$$ distribution is associated with a $$\chi^2$$ test. Use the $$\chi^2$$ test to compare observed and expected values.
This means that the p-value displayed by the function will be lower when the observed valuer are far away from the expected ones; and the p-value will be $$1$$ if the observed values match exactly the expected values. Therefore, since you are getting a very small p-value (displayed as zero due to the rounding done by Excel), I deduct that your data is distinct from the expected distribution.
• @DimitrisM : 2.7 million is a lot! Are you sure you haven't made a mistake? For 74 degrees of freedom, a p-value of $0.001$ would be attained for $\chi^2$ around $117$; and a p-value of $10^{-30}$ would be attained for $\chi^2$ around $310$. – Ertxiem - reinstate Monica Oct 1 '19 at 22:25
• @DimitrisM: I've checked your data and I got $\chi^2 = 2\ 189 \ 770.58$ for $df=74$. So, It's natural to have such a low p-value. Looking at the data, you see counties with an incidence of nearly $43\%$, and others with incidences of $0.01\%$, thus, the p-value is telling that there are significant differences between counties, which is according to what is observed. – Ertxiem - reinstate Monica Dec 17 '19 at 22:28