Step 5 - Interpreting The Results | chi square value meaning
Statisticianscalculatecertainpossibilitiesofoccurrence(Pvalues)foraX2 valuedependingon degreesoffreedom[1].Degreesoffreedomissimplythenumberofclassesthatcanvaryindependentlyminusone,(n-1).Inthiscasethedegreesoffreedom=1becausewehave2phenotypeclasses:resistantandsusceptible.ThecalculatedvalueofX2 fromourresultscanbecomparedtothevaluesinthetablealignedwiththespecificdegreesoffreedomwehave.Thiswilltellustheprobabilitythatthedeviations(betweenwhatwe expected[2] toseeandwhatweactuallysaw)aredueto...
Statisticians calculate certain possibilities of occurrence (P values) for a X2 value depending on degrees of freedom[1]. Degrees of freedom is simply the number of classes that can vary independently minus one, (n-1). In this case the degrees of freedom = 1 because we have 2 phenotype classes: resistant and susceptible.
The calculated value of X2 from our results can be compared to the values in the table aligned with the specific degrees of freedom we have. This will tell us the probability that the deviations (between what we expected[2] to see and what we actually saw) are due to chance alone and our hypothesis or model can be supported.
In our example, the X2 value of 1.2335 and degrees of freedom of 1 are associated with a P value of less than 0.50, but greater than 0.25 (Follow blue dotted line and arrows in Fig 5). This means that a chi-square[3] value this large or larger (or differences between expected and observed[4] numbers this great or greater) woul...