Normal distribution

Question

Suppose we are told that weights of 1-year-old boys are approximately normally distributed, with a mean of 22.8 lbs and a standard deviation of about 2.15. (Source: About.com) If we randomly select a 1-year-old boy, what is the probability that he'll weigh at least 20 pounds?

Answer 1

You need a z table to find probability to the right (If the table give values to the left: P(right) = 1 = P(left))

z = (x -μ)/σ x is 20, μ = 22.8 σ = 2.15

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