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A normal distribution has a mean of 15 and a standard deviation of 3. What interval contains approximately 95% of the data, according to the Empirical Rule?

Mathematics

ScanSolve AI Answer

Answer

e

b) 9-21\text{b) 9-21}

Step-by-step solution

2 steps

This problem uses the Empirical Rule (also known as the 68-95-99.7 rule) for normal distributions. This rule states that for a normal distribution:

  • Approximately 68% of the data falls within 1 standard deviation of the mean.
  • Approximately 95% of the data falls within 2 standard deviations of the mean.
  • Approximately 99.7% of the data falls within 3 standard deviations of the mean.

We are given:

  • Mean (μ\mu) = 15
  • Standard deviation (σ\sigma) = 3

We need to find the interval that includes about 95% of the probability. According to the Empirical Rule, this interval is μ±2σ\mu \pm 2\sigma.

  1. Calculate the lower bound of the interval.

    Lower bound=μ−2σ=15−2(3)=15−6=9\text{Lower bound} = \mu - 2\sigma = 15 - 2(3) = 15 - 6 = 9
  2. Calculate the upper bound of the interval.

    Upper bound=μ+2σ=15+2(3)=15+6=21\text{Upper bound} = \mu + 2\sigma = 15 + 2(3) = 15 + 6 = 21

    The interval that includes about 95% of the probability is 9-21.

    Comparing this result with the given options:

    a) 12-18

    b) 9-21

    c) 6-24

    d) 3-27

    e) none of the above

    The calculated interval matches option (b).

    The final answer is b) 9-21\boxed{\text{b) 9-21}}.

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