What is a pooled variance?

Emilio Calhoun

Emilio Calhoun

Answered question

2022-10-13

What is a pooled variance?

Answer & Explanation

Davion Fletcher

Davion Fletcher

Beginner2022-10-14Added 9 answers

Let consider we have two sets of data with n 1 and n 2 size. Also consider their variances as s 1 2 and s 2 2 . Then pooled variance means the variance of combined data sets with size n 1 + n 2 and it is defined as
( n 1 - 1 ) s 1 2 + ( n 2 - 1 ) s 2 2 n 1 + n 2 - 2
You can combine more than two data sets also. If you have data sets with sizes n 1 , n 2 ... . n k and variances s 1 2 , s 2 2 ... . s k 2 then pooled variance is defined as
( n 1 - 1 ) s 1 2 + ( n 2 - 1 ) s 2 2 + ... + ( n k - 1 ) s k 2 n 1 + n 2 + ... + n k - k

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