Math Problem Statement

You intend to estimate a population mean μ with the following sample. 82.7, 95.2, 93.2, 56.9, 81.6, 84.7, 85.1, 94.5, 109.5, 72.3 You believe the population is normally distributed. Find the 99% confidence interval. Enter your answer as an open-interval (i.e., parentheses) accurate to two decimal places (because the sample data are reported accurate to one decimal place).

Solution

To calculate a 99% confidence interval for the population mean μ\mu based on a sample, we follow these steps:

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

The sample data is: 82.7,95.2,93.2,56.9,81.6,84.7,85.1,94.5,109.5,72.382.7, 95.2, 93.2, 56.9, 81.6, 84.7, 85.1, 94.5, 109.5, 72.3

xˉ=82.7+95.2+93.2+56.9+81.6+84.7+85.1+94.5+109.5+72.310\bar{x} = \frac{82.7 + 95.2 + 93.2 + 56.9 + 81.6 + 84.7 + 85.1 + 94.5 + 109.5 + 72.3}{10}

Step 2: Calculate the sample standard deviation (ss)

s=(xixˉ)2n1s = \sqrt{\frac{\sum (x_i - \bar{x})^2}{n - 1}}

Step 3: Find the t-score for a 99% confidence level with n1=9n - 1 = 9 degrees of freedom

Using the t-distribution table for a 99% confidence level and 9 degrees of freedom, we find the t-score.

Step 4: Calculate the margin of error (ME)

ME=t×sn\text{ME} = t \times \frac{s}{\sqrt{n}}

Step 5: Determine the confidence interval

Confidence Interval=(xˉME,xˉ+ME)\text{Confidence Interval} = \left( \bar{x} - \text{ME}, \bar{x} + \text{ME} \right)

I'll compute these values.The 99% confidence interval for the population mean μ\mu based on the given sample is approximately:

(70.93,100.21)(70.93, 100.21)

This interval suggests that we are 99% confident that the population mean lies within this range.

Would you like further details on this process or have any questions?

Here are five related questions to explore further:

  1. How would the confidence interval change with a 95% confidence level?
  2. What would the confidence interval be if we had a larger sample size?
  3. How does the standard deviation of the sample affect the confidence interval width?
  4. What assumptions are made when using a t-distribution for confidence intervals?
  5. How would the interval differ if we assumed the population standard deviation was known?

Tip: Remember, increasing the confidence level increases the interval width, as higher confidence requires capturing more possible values for the population mean.

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Math Problem Analysis

Mathematical Concepts

Statistics
Confidence Interval
Sample Mean
t-Distribution

Formulas

Sample mean: \( \bar{x} = \frac{\sum x}{n} \)
Sample standard deviation: \( s = \sqrt{\frac{\sum (x_i - \bar{x})^2}{n - 1}} \)
Margin of error: \( \text{ME} = t \times \frac{s}{\sqrt{n}} \)
Confidence interval: \( (\bar{x} - \text{ME}, \bar{x} + \text{ME}) \)

Theorems

Central Limit Theorem
Properties of the t-Distribution

Suitable Grade Level

Grades 11-12