"first we fill out the 2 x 2 table as if there were no association ("expected values", Ei). Divide the cases and controls (proportionally) into the four cells of the contingency table."
"then fill in the actual values that you found from your study ("observed values", Oi)."
"this is the [Oi - Ei] per cell."
"χ2 = Σ ([Oi - Ei]2 / Ei)"
"This results in a chi-squared number (χ2), which can be checked in a table for significance. The degree of freedom for a 2 x 2 table is 1. If the χ2 value is above the level in the table, then we can reject the null hypothesis (no association between the variables)."
"This results in a chi-squared number (χ2), which can be checked in a table for significance. The degree of freedom for a 2 x 2 table is 1. If the χ2 value is above the level in the table, then we can reject the null hypothesis (no association between the variables)."
Expected headings
"Concept"
"Points"
"chi-squared tests work with categorical variables (e.g. disease vs no disease, got imaging test vs did not get imaging test, etc)"
"it is not meant for continuous variables (e.g. length, time, radiation dose, etc)"