11.2 The Chi-Square Test for Goodness-of-Fit

chi-square statistic

can be used to test whether the observed counts match the counts we expect according to some model - equation is χ² =
∑_{all cells} (Obs-Exp)² / Exp

chi-square component

the components of a chi-square calculation are (Obs-Exp)² / Exp, found for each cell of the table

expected counts

the distribution of counts into groups as would be expected if they were distributed completely perfectly

cell

one element of a table, which corresponds to a specific row and column - table cells can hold counts, percentages, measurements on other variables, or several values

goodness-of-fit

an idea for testing whether a group of counts is distributed in a way that is expected or not

chi-square model

these are skewed to the right, and parameterized by their degrees of freedom, becoming less skewed with increasing degrees of freedom