Question

A researcher is interested in estimating the mean weight of a semi tracker tractor truck to determine the potential load capacity. She takes a random sample of 17 trucks and computes a sample mean of 20,000 pounds with sample standard deviation of 1,500. The 95% confidence interval for the population mean weight of a semi tracker tractor truck is ______________.

Answer 1

(19228.737 ; 20771.263)

Explanation:

Given that:

Sample size, n = 17

Sample mean, m = 20,000

Sample standard deviation, s = 1500

α = 95%

The confidence interval,

Mean ± margin of error

Margin of Error : Tcritical * s/sqrt(n)

Tcritical at α = 0.05 ; df = n-1 = 17 - 1 = 16 ; 2 - tailed test = 2.120

Margin of Error = 2.120 * 1500/sqrt(17) = 771.263

Lower boundary :

20,000 - 771.263 = 19228.737

Upper boundary :

20,000 + 771.263 = 20771.263

Confidence interval :

(19228.737 ; 20771.263)