MathBench > Statistical Tests - Chi | Chi-square critical value
Onceyouknowthedegreesoffreedom(ordf), youcanuseachisquaretable,liketheoneontheright(bookssometimeshaveamore complicatedtablewhichwelltalkaboutatthebottomofthepage). Althoughthistabledoescomefromamathematicalfunction(calledachi-square distribution,gofigure!)forourpurposesyoucanbasicallytreatitlikeit appearedmagically. Thefirstthingyouneedtoknowisthedegreesoffreedominyourtest.Aswetalked aboutonthelastpage,thisisthesameasthenumberofrowsinyourtableminus1. Useyourd...
Once you know the degrees of freedom (or df), you can use a chi square table, like the one on the right (books sometimes have a more complicated table which well talk about at the bottom of the page).
Although this table does come from a mathematical function (called a chi-square distribution, go figure!) for our purposes you can basically treat it like it appeared magically.
The first thing you need to know is the degrees of freedom in your test. As we talked about on the last page, this is the same as the number of rows in your table minus 1. Use your df to look up the critical value of the chi-square test, also called the chi-square-crit. So for a test with 1 df (degree of freedom), the "critical" value of the chi-square statistic is 3.84.
What does critical value mean?
Basically, if the chi-square you calculated...