In an experiment with 15 observations for x , the following results were available x^2=2830, x=170 . One observation 20 was found to be wrong and was replaced by the correct value 30 . Then the corrected variance is

Step-by-step solution

Given: x=170 and x^2=2830 Corrected sum aligned & x=170-20+30=180 & x^2=2830-400+900=3330 aligned Corrected variance aligned & = ( x^2 n )- ( x n )^2 & = ( 3330 15 )- ( 180 15 )^2 & =222-144=78 aligned