Question

An environmental group at a local college is conducting independent tests to determine the distance a particular make of automobile will travel while consuming only 1 gallon of gas. They test a sample of five cars and obtain a mean of 28.2 miles. Assuming that the standard deviation is 2.7 miles, find the 95 percent confidence interval for the mean distance traveled by all such cars using 1 gallon of gas.

Answer 1

Answer:

$26.5265$

Step-by-step explanation:

Confidence Interval

When the population standard deviation $\sigma$ is known, the formula for a confidence interval for a population mean $\bar x$ is:

$\displaystyle \bar x \pm z\frac{\sigma}{\sqrt{n}}$

Where n is the sample size and z is the corresponding z-value from the standard normal distribution for the selected confidence level. The value of z for a 95% confidence interval is z=1.96. The rest of the values are

$\bar x=28.2,\ \sigma=2.7, \ n=10$

Calculating the confidence interval

$\displaystyle 28.2 \pm 1.96\frac{2.7}{\sqrt{10}}$

$\displaystyle 28.2 \pm 1.6735$

Or, equivalently

$26.5265$