Math Problem Statement

Suppose you are told that a 95% confidence interval for the average price of a gallon of regular gasoline in your state is from $4.06 to $4.56. Use the fact that the confidence interval for the mean is in the form x − E to x + E to compute the sample mean and the maximal margin of error E.

What is the sample mean (in dollars)?

What is the maximal margin of error (in dollars)?

Solution

To solve this problem, we need to use the information provided about the confidence interval. The confidence interval is given as $4.06 to $4.56, and we know it is in the form xˉE\bar{x} - E to xˉ+E\bar{x} + E, where:

  • xˉ\bar{x} is the sample mean.
  • EE is the maximal margin of error.

Step 1: Calculate the sample mean (xˉ\bar{x})

The sample mean xˉ\bar{x} is the midpoint of the confidence interval. We calculate it by taking the average of the lower and upper bounds of the interval:

xˉ=4.06+4.562=8.622=4.31\bar{x} = \frac{4.06 + 4.56}{2} = \frac{8.62}{2} = 4.31

So, the sample mean xˉ\bar{x} is $4.31.

Step 2: Calculate the maximal margin of error (EE)

The maximal margin of error EE is the difference between the sample mean xˉ\bar{x} and either endpoint of the confidence interval. We can calculate it by subtracting the sample mean from the upper bound:

E=4.564.31=0.25E = 4.56 - 4.31 = 0.25

Thus, the maximal margin of error EE is $0.25.

Final Answers:

  • Sample mean: $4.31
  • Maximal margin of error: $0.25

Would you like to explore any details or have any questions about this problem?


Here are 8 related questions you might consider:

  1. How does the confidence level affect the width of the confidence interval?
  2. What happens to the margin of error if the sample size increases?
  3. How would a 99% confidence interval for the same data compare in width to the 95% interval?
  4. What role does the standard deviation play in determining the margin of error?
  5. How can we use this interval to estimate the population mean with a higher or lower confidence level?
  6. What is the formula for the margin of error in a confidence interval?
  7. How does the confidence interval change if the variability of the data increases?
  8. What assumptions are made about the data when calculating a confidence interval?

Tip: The margin of error is directly influenced by the sample size and variability of the data; larger sample sizes typically result in smaller margins of error.

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Math Problem Analysis

Mathematical Concepts

Statistics
Confidence Interval

Formulas

Confidence interval for the mean: x - E to x + E

Theorems

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Suitable Grade Level

Advanced High School