# A confidence interval of the mean

Not what you're looking for?

This problem is solved:

Let's summarize the method for finding the 95% confidence interval using a step-by-step illustration. Suppose that a certain automobile company wishes to determine the expected miles per gallon for one of its new models. Based on years of experience with cars, the company statistician realizes that not all cars are equal, and that a standard deviation of 4 miles per gallon ( = 4) is to be expected due to variations in parts and workmanship. In order to estimate the mean miles per gallon for the new model, he test runs a random sample of 100 cars off the assembly line and obtains a sample mean of 26 miles per gallon.

What steps are followed to obtaining a 95% confidence interval for the mean miles per gallon for all cars of this model?

##### Purchase this Solution

##### Solution Summary

Steps are given to solve this problem.

##### Solution Preview

STEP 1

Obtain the mean for a random sample (in this problem, it is given).

N=100, X=26

STEP 2

Calculate the standard error of the mean (knowing that standard deviation = 4).

standard error of the mean

= ...

##### Purchase this Solution

##### Free BrainMass Quizzes

##### Measures of Central Tendency

Tests knowledge of the three main measures of central tendency, including some simple calculation questions.

##### Measures of Central Tendency

This quiz evaluates the students understanding of the measures of central tendency seen in statistics. This quiz is specifically designed to incorporate the measures of central tendency as they relate to psychological research.

##### Terms and Definitions for Statistics

This quiz covers basic terms and definitions of statistics.

##### Know Your Statistical Concepts

Each question is a choice-summary multiple choice question that presents you with a statistical concept and then 4 numbered statements. You must decide which (if any) of the numbered statements is/are true as they relate to the statistical concept.