Posted by **Mary** on Friday, January 16, 2009 at 4:21am.

A set of data is normally distributed with a mean of 500 and standard deviation of 40.

a). What percent of the data is between 460 and 540?

P(460<x<540)=P(-1<z<1)

=0.8413-0.1587

=0.6826

b). Find the probabilty that a value selected at random is less than 420.

P(x<420)=P(z<(420-500)/40)

=P(z<-2)

=0.0228

are these right?

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