High School

Assume the weight of all adults in the United States is normally distributed with a mean of 160 lbs and a standard deviation of 15 lbs. If person A weighs 145 lbs, which part under the normal curve should be shaded if we want to know the percentage of people heavier than person A?

Answer :

The percentage of people heavier than person A is approximately 100% - (0.8413 100%) = 15.87%.

First, we need to calculate the z-score for person A's weight. The z-score measures the number of standard deviations person A's weight is away from the mean.

The formula to calculate the z-score is:

z = (x - μ) / σ

Where:

- x is the value we want to convert to a z-score (person A's weight)

- μ is the mean of the distribution (160 lbs)

- σ is the standard deviation of the distribution (15 lbs)

Substituting the values:

z = (145 - 160) / 15

z = -1

Now, we need to find the area to the right of the z-score of -1 on the standard normal distribution table or using a calculator.

The area to the right of z = -1 is equal to the area to the left of z = 1 (since the total area under the curve is 1).

Using a standard normal distribution table or calculator, we find that the area to the left of z = 1 is approximately 0.8413.

Therefore, the percentage of people heavier than person A is approximately 100% - (0.8413100%) = 15.87%.

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