Question

Estimate the population mean by finding a 80% confidence interval given a sample of size 635, with a mean of 78.9 and a standard deviation of 9.5.

Preliminary:

1. Is it safe to assume that n≤0.05 of all subjects in the population?
   • No
   • Yes
   
   
2. Is n≥30
   • No
   • Yes

Confidence Interval: What is the 80% confidence interval to estimate the population mean? Enter the tri-linear inequality values accurate to one decimal place.

<μ<

Answer 1

Given that, sample size (n) = 635, sample mean = 78.9 and

standard deviation = 9.5

Preliminary : Yes it is safe to assume that n ≤ 0.05 of all subjects in the population.

Yes, n = 645 ≥ 30

Confidence Interval :

A 80% confidence level has significance level of 0.20 and critical value is,

The 80% confidence interval for the population mean is,

Answer : 78.4 < μ < 79.4