I URGENTLY NEED HELP WITH THIS PLEASE!!!!

Question

Kind of lost here!!!!

 

An IQ test is designed so that the mean is 100 and the standard deviation is 18 for the population of normal adults. Find the sample size necessary to estimate the mean IQ score of statistics students such that it can be said with 95% confidence that the sample mean is within 3 IQ points of the true mean. Assume that σ =18 and determine the required sample size using technology.

Then determine if this is a reasonable sample size for a real world calculation.

The required sample size is ?. (Round up to the nearest integer.)

 

Answer 1

n=(σ z_α/2/e)² ; e=3

 

confidence interval is 95% then α=1-0.95=0.05

 

z_0.05/2=z_0.025=1.96 (you can find the value from Normal curve table)

n=(18*1.96/3)²=138.3 ≈ 139

 

the sample size should be 139