Math Problem Statement

95% of students are between 1.1 m and 1.7 m tall. What is the mean and standard deviation?

Solution

In a normal distribution, about 95% of the data falls within two standard deviations (±2σ) of the mean (μ). This is known as the empirical rule.

Given:

  • 95% of the students are between 1.1 m and 1.7 m tall.
  • Therefore, the range 1.1 m to 1.7 m represents μ - 2σ to μ + 2σ.

We can set up two equations:

  • μ2σ=1.1\mu - 2\sigma = 1.1
  • μ+2σ=1.7\mu + 2\sigma = 1.7

Solving for μ and σ:

  1. Add both equations:
    (μ2σ)+(μ+2σ)=1.1+1.7(\mu - 2\sigma) + (\mu + 2\sigma) = 1.1 + 1.7 2μ=2.8μ=1.4m2\mu = 2.8 \quad \Rightarrow \quad \mu = 1.4 \, \text{m}

  2. Subtract the first equation from the second: (μ+2σ)(μ2σ)=1.71.1(\mu + 2\sigma) - (\mu - 2\sigma) = 1.7 - 1.1 4σ=0.6σ=0.15m4\sigma = 0.6 \quad \Rightarrow \quad \sigma = 0.15 \, \text{m}

Final answer:

  • Mean (μ) = 1.4 m
  • Standard deviation (σ) = 0.15 m

Would you like more details or have any questions?

Here are 5 related questions:

  1. How does the empirical rule help in understanding normal distributions?
  2. What percentage of students would be taller than 1.7 m?
  3. How would the distribution change if the standard deviation were larger?
  4. What would the range be if only 68% of the students were considered?
  5. How do mean and standard deviation affect the shape of a normal distribution?

Tip: In a normal distribution, around 68% of data falls within 1 standard deviation of the mean, and 99.7% within 3 standard deviations.

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Math Problem Analysis

Mathematical Concepts

Normal Distribution
Empirical Rule
Standard Deviation
Mean

Formulas

μ - 2σ = 1.1
μ + 2σ = 1.7
2μ = 2.8 → μ = 1.4
4σ = 0.6 → σ = 0.15

Theorems

Empirical Rule (68-95-99.7 Rule)

Suitable Grade Level

Grades 9-12