Question

Assume that the average water bill is $15.30 with standard deviation $4.10.

a) What is the probability that in a random sample of 36 people in a particular neighborhood

their average water bill is $14.00 or less.

b) What is the smallest range of water bill amounts covering 99% of the distribution?

Answer 1

Solution Given that, u= 15.30 6 - 4.10 n = 36 Mx = 1= 15.30 P (*<14.00) -Pfalt < 150 1530) -P(Z <= 132 ) – P(Z <-1.91) P(x<19.00] =0.0281 probability is 0.0281

b) The 2 distribution of the 99% is P(Z <z) = 99% P(Z < 2 ) = 0.99 P(Z <2.33) = 0.99 Z = 2:33 2 score formulla X - Zot u x = 2.33 X 4.10 + 15.30 x = 24.85 The smallest range of water bill amount = 24.85 is,