Question

Mean of 100 observations is 40 the 9th observation is 30 if this replaced by 70 keeping all other observation same find the mean

Answer 1

Mean of 100 obs=40

Sum of obs=40*100=4000

if 9th observation is 30 and replaced with 70

So, Sum of obs=4000—30+70=4040

Hence,New mean=4040/100=40.4