Suppose the number of square feet per house is normally distributed. If the population standard deviation is155

square feet, what minimum sample size is needed to be90%

confident that the sample mean is within47

square feet of the true population mean?

z

0.10

1.282

z

0.05

1.645

z

0.025

1.960

z

0.01

2.326

z

0.005

2.576

Use the table above for thez

-score, and be sure to round up to the next integer.