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Exercises Probability and the bell curve

Example 6.11 from Statistics, 6.2 Using the Normal Distribution

(part 2)

b. Forty percent of the ages that range from 13 to 55+ are at least what age?

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

1
Solution
b.
- Find k where P(x ≥ k) = 0.40. At least translates to greater than or equal to.
- 0.40 = the area to the right
- The area to the left = 1 – 0.40 = 0.60.
- The area to the left of k = 0.60
- invNorm(0.60,36.9,13.9) = 40.4215
- k = 40.4.
- Forty percent of the ages that range from 13 to 55+ are at least 40.4 years.

How did it go?

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From Statistics (High school edition) by OpenStax (Rice University), section 6.2, licensed under CC BY 4.0. Original at openstax.org. We split the solution into steps; the words, numbers and figures are the book's. OpenStax doesn't endorse this site.