Math Problem Statement

Natalie ran an experiment to test optimum power and time settings for microwave popcorn. Her goal was to deliver popcorn with fewer than 10% of the kernels left unpopped, on average. She determined that power 9 at 4 minutes was the best combination. To be sure that the method was successful, she popped 8 more bags of popcorn (selected at random) at this setting, and recorded the percentages of unpopped kernels for each bag: 6.9, 3.4, 9.5, 4.3, 8.7, 10.9, 5.1, 5.3. Does this provide evidence that she met her goal of an average of fewer than 10% unpopped kernels? Use 0.05 as the P-value cutoff level.

Solution

To determine if Natalie met her goal, we need to conduct a one-sample t-test with the following hypotheses:

  1. Null Hypothesis (H₀): μ=10\mu = 10 (The average percentage of unpopped kernels is 10%).
  2. Alternative Hypothesis (Hₐ): μ<10\mu < 10 (The average percentage of unpopped kernels is less than 10%).

Since option B is selected, it correctly represents these hypotheses.

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

The sample data consists of percentages of unpopped kernels from 8 bags: 6.9,3.4,9.5,4.3,8.7,10.9,5.1,5.36.9, 3.4, 9.5, 4.3, 8.7, 10.9, 5.1, 5.3

Calculate the mean (xˉ\bar{x}) of these values: xˉ=6.9+3.4+9.5+4.3+8.7+10.9+5.1+5.38\bar{x} = \frac{6.9 + 3.4 + 9.5 + 4.3 + 8.7 + 10.9 + 5.1 + 5.3}{8}

Step 2: Calculate the sample standard deviation (ss)

We find the standard deviation of the sample data to use in the t-test.

Step 3: Calculate the t-statistic

The t-statistic is given by: t=xˉμsnt = \frac{\bar{x} - \mu}{\frac{s}{\sqrt{n}}} where:

  • xˉ\bar{x} is the sample mean,
  • μ=10\mu = 10 (hypothesized mean),
  • ss is the sample standard deviation,
  • n=8n = 8 (sample size).

Let me know if you'd like a step-by-step calculation for these values or if you have further questions.


Here are five related questions:

  1. What are the assumptions for conducting a t-test?
  2. How does changing the significance level (e.g., from 0.05 to 0.01) affect the test result?
  3. What is a Type I error in hypothesis testing?
  4. How would the test change if we suspected the mean was higher than 10% instead?
  5. How can we interpret the p-value obtained from this test?

Tip: Always check if the sample size is adequate for a t-test, especially for small samples where normality is assumed.

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Math Problem Analysis

Mathematical Concepts

Statistics
Hypothesis Testing
One-sample t-test

Formulas

Sample mean \( \bar{x} = \frac{\sum x}{n} \)
Sample standard deviation \( s = \sqrt{\frac{\sum (x - \bar{x})^2}{n - 1}} \)
t-statistic \( t = \frac{\bar{x} - \mu}{\frac{s}{\sqrt{n}}} \)

Theorems

One-sample t-test

Suitable Grade Level

College-level Statistics