Elementary Statistics and Computer Application

2x2 – contingency table

• When the number of rows and numberof columns are equal to 2 it is termed as 2 x 2 contingency table . It will be in the following form
• Where a, b, c and d are cell frequancies c1 and c2 are column totals, r1 and r2 are row totals and n is the total number of observations.
• In case of 2 x 2 contigency table can be directly found using the short cut formula,
 

• The d.f associated with is (2-1) (2-1) =1
 
Yates correction for continuity

• If anyone of the cell frequency is < 5, we use Yates correction to make as continuous. The yares correction is made by adding 0.5 to the least cell frequency and adjusting the other cell frequencies so that the column and row totals remain same . suppose, the firat cell frequency is to be corrected then the consigency table will be as follows
• Then use the - statistic as

• The d.f associated with is (2-1) (2-1) =1