In: Statistics and Probability
A survey found that the American family generates an average of 17.2 pounds of glass garbage each year. Assume population is normally distributed with standard deviation of 2.5 pounds. Find the probability that the mean of a sample of 55 families will generate between 17 and 18 pounds.
Solution :
Given that ,
mean = = 17.2
standard deviation = = 2.5
n = 55
= 17.2
= / n= 2.5 / 55=0.34
P(17< <18 ) = P[(17-17.2) / 0.34< ( - ) / < (18-17.2) /0.34 )]
= P(-0.59 < Z < 2.35)
= P(Z< 2.35 ) - P(Z <-0.59 )
Using z table
=0.9906 - 0.2776
=0.7130
probability= 0.7130