What is the z-score of sample X, if #n = 144, mu= 71, St. Dev. =12, and E[X] =77#?

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Answer 1 · 2016-12-01T19:41:08

The z-score is #=6#

The z-score of a sample mean is

#z=(barx-mu)/(sigma/sqrtn)#

#barx=E [X]=77#

#mu=71#

#sigma=12#

#n=144#

Therefore,

#z=(77-71)/(12/sqrt144)=6/(12/12)=6#