Math Problem Statement

Seventy million pounds of trout are grown in the U.S. every year. Farm-raised trout contain an average (mean) of 32 grams of fat per pound, with a standard deviation of 7.5 grams of fat per pound. A random sample of 36 farm-raised trout is selected. The mean fat content for the sample is 29.7 grams per pound. Find the probability of observing a sample mean of 29.7 grams of fat per pound or less in a random sample of 36 farm-raised trout.

Solution

To solve this problem, we need to find the probability that the sample mean is 29.7 grams or less in a random sample of 36 farm-raised trout. This involves using the Central Limit Theorem and the properties of the normal distribution.

Here's the approach:

  1. Given data:

    • Population mean μ=32\mu = 32 grams
    • Population standard deviation σ=7.5\sigma = 7.5 grams
    • Sample size n=36n = 36
    • Sample mean xˉ=29.7\bar{x} = 29.7 grams
  2. Standard error of the mean: The standard error (SE) is calculated as: SE=σn=7.536=7.56=1.25SE = \frac{\sigma}{\sqrt{n}} = \frac{7.5}{\sqrt{36}} = \frac{7.5}{6} = 1.25

  3. Z-score calculation: We now calculate the Z-score, which is the number of standard errors the sample mean is away from the population mean: Z=xˉμSE=29.7321.25=2.31.25=1.84Z = \frac{\bar{x} - \mu}{SE} = \frac{29.7 - 32}{1.25} = \frac{-2.3}{1.25} = -1.84

  4. Finding the probability: Using the Z-table or a calculator, find the probability corresponding to a Z-score of 1.84-1.84.

    The probability for Z1.84Z \leq -1.84 is approximately 0.0329 (from the Z-table).

Thus, the probability that the sample mean is 29.7 grams or less is 0.0329 or 3.29%.

Would you like further clarification or more details on any step?

Here are 5 related questions to expand your understanding:

  1. What is the Central Limit Theorem and how does it apply to this problem?
  2. How would the probability change if the sample size increased?
  3. What is the significance of the Z-score in normal distribution problems?
  4. Why do we use the standard error instead of the population standard deviation when working with sample means?
  5. How would the result differ if the population had a non-normal distribution?

Tip: When solving problems involving the Central Limit Theorem, always check if the sample size is large enough to assume normality for the sample mean distribution.

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Math Problem Analysis

Mathematical Concepts

Probability
Normal Distribution
Central Limit Theorem

Formulas

Standard Error: SE = σ / sqrt(n)
Z-score: Z = (x̄ - μ) / SE

Theorems

Central Limit Theorem

Suitable Grade Level

Grades 10-12 (High School Statistics)