Math Problem Statement

The distribution of the number of daily requests is bell-shaped and has a mean of 39 and a standard deviation of 11. Using the empirical rule, what is the approximate percentage of lightbulb replacement requests numbering between 17 and 39?

Do not enter the percent symbol. ans = %

Solution

The empirical rule, also known as the 68-95-99.7 rule, states that for a bell-shaped distribution (normal distribution):

  1. About 68% of the data lies within 1 standard deviation of the mean.
  2. About 95% of the data lies within 2 standard deviations of the mean.
  3. About 99.7% of the data lies within 3 standard deviations of the mean.

Given:

  • Mean (μ\mu) = 39
  • Standard deviation (σ\sigma) = 11
  • Range: Between 17 and 39

Now, let's find how many standard deviations away from the mean the value of 17 is: z=391711=2z = \frac{39 - 17}{11} = 2 So, 17 is 2 standard deviations below the mean.

According to the empirical rule, about 95% of the data lies within 2 standard deviations of the mean. Since the range 17 to 39 represents half of this (from the mean to 2 standard deviations below it), the percentage of requests in this range is: 95%2=47.5%\frac{95\%}{2} = 47.5\%

Thus, the approximate percentage is 47.5\boxed{47.5}.

Would you like more details, or do you have any other questions?

Here are five related questions:

  1. What percentage of requests fall between 28 and 50 using the empirical rule?
  2. How can the empirical rule be applied to a dataset with different mean and standard deviation?
  3. What is the percentage of requests falling below 17 using the empirical rule?
  4. What would the range be for 68% of the requests?
  5. How does the empirical rule differ from exact probabilities in a normal distribution?

Tip: The empirical rule is most accurate for perfectly normal distributions but gives a good approximation for many real-world data sets.

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Math Problem Analysis

Mathematical Concepts

Statistics
Normal Distribution
Empirical Rule

Formulas

z = (x - μ) / σ
Empirical rule: 68-95-99.7 rule

Theorems

Empirical Rule (68-95-99.7 rule)

Suitable Grade Level

Grades 9-12