Math Problem Statement

You must estimate the mean temperature (in degrees Fahrenheit) with the following sample temperatures: 3.2, 36.7, 44.7, 23, 26.5, 51.7, 16.6, 44.1, 16.2, 28.4, 62.3, 75.8. Find the 90% confidence interval. Enter your answer as an open-interval (i.e., parentheses) accurate to 3 decimal places. Assume the data is from a normally distributed population.

Solution

To calculate the 90% confidence interval for the mean temperature, let's go through these steps:

  1. Calculate the Sample Mean (xˉ\bar{x}): Add up all the sample values and divide by the number of samples.

  2. Calculate the Sample Standard Deviation (s): Use the formula s=(xixˉ)2n1s = \sqrt{\frac{\sum (x_i - \bar{x})^2}{n-1}}, where xix_i is each individual sample, xˉ\bar{x} is the sample mean, and nn is the sample size.

  3. Determine the Confidence Interval: For a 90% confidence interval with a normally distributed population and unknown population standard deviation, use the t-distribution:

    Margin of Error=tα/2sn\text{Margin of Error} = t_{\alpha/2} \cdot \frac{s}{\sqrt{n}}

    where tα/2t_{\alpha/2} is the t-score for a 90% confidence level with n1n-1 degrees of freedom, ss is the sample standard deviation, and nn is the sample size.

  4. Calculate the Interval: The confidence interval is given by:

    (xˉMargin of Error,xˉ+Margin of Error)\left( \bar{x} - \text{Margin of Error}, \bar{x} + \text{Margin of Error} \right)

Let’s compute this based on the data provided:

Data Provided:

Temperatures: 3.2,36.7,44.7,23,26.5,51.7,16.6,44.1,16.2,28.4,62.3,75.83.2, 36.7, 44.7, 23, 26.5, 51.7, 16.6, 44.1, 16.2, 28.4, 62.3, 75.8

I’ll calculate the values now.The 90% confidence interval for the mean temperature, accurate to three decimal places, is:

(24.909,46.624)(24.909, 46.624)

Would you like more details or have any questions?

Here are five related questions that may help deepen your understanding:

  1. How would the confidence interval change with a different confidence level, such as 95%?
  2. What is the interpretation of a 90% confidence interval in this context?
  3. How does the sample size affect the width of the confidence interval?
  4. What is the role of the t-score, and why is it used instead of the z-score?
  5. How would outliers in the data affect the confidence interval?

Tip: A larger sample size will typically result in a narrower confidence interval, assuming the sample represents the population well.

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Math Problem Analysis

Mathematical Concepts

Statistics
Confidence Interval
Mean Estimation
T-distribution

Formulas

Sample Mean (\( \bar{x} = \frac{\sum x_i}{n} \))
Sample Standard Deviation (\( s = \sqrt{\frac{\sum (x_i - \bar{x})^2}{n-1}} \))
Margin of Error (\( \text{Margin of Error} = t_{\alpha/2} \cdot \frac{s}{\sqrt{n}} \))
Confidence Interval (\( (\bar{x} - \text{Margin of Error}, \bar{x} + \text{Margin of Error}) \))

Theorems

Central Limit Theorem

Suitable Grade Level

Undergraduate Statistics