Chi-square goodness of fit calculator

Calculate chi-square statistic and degrees of freedom with your own figures.

Your numbers

Use the units shown. Results update as you change valid inputs.

Use chi-square statistic and degrees of freedom to compare changes to your inputs. The method and limits below explain the scope.

Examples

Examples

Try the starting example

Observed counts
10,20
Expected counts
15,15
Chi-square statistic
3.333333
Degrees of freedom
1
Upper-tail p-value
0.067889

Try another scenario

Observed counts
8,22
Expected counts
15,15
Chi-square statistic
6.533333
Degrees of freedom
1
Upper-tail p-value
0.010587
Calculation method

Calculation method

Chi-square statistic

Sum (observed−expected)²/expected across categories; expected totals must equal observed totals.

Degrees of freedom

Number of categories minus one, assuming no parameters were fitted to these observations.

Upper-tail p-value

Upper-tail chi-square probability Q(df/2, statistic/2).

Symbols and units
a
Observed counts
b
Expected counts

Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.

Assumptions & limits

Assumptions & limits

  • Reports the chi-square statistic, degrees of freedom and an upper-tail p-value. Expected counts must have the same total; fitted-parameter adjustments are not included. Lists support up to 1,000 finite values. The p-value uses an asymptotic chi-square model with fixed expected proportions and no fitted parameters; sparse expected counts can make the approximation unreliable.
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Further reading

Method reference ↗

Background reading; this does not imply endorsement or independent review of SumFizz.

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