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Given an approximately normal distribution with a mean of 175 and a standard deviation of 37.

(a) Draw a normal curve and label 1, 2, and 3 standard deviations on both sides on the mean.

(b) What percent of values are within the interval (138, 212)?

(c) What percent of values are within the interval (101, 249)?

(d) What percent of values are within the interval (64, 286)?

(e) What percent of values outside the interval (138, 212)?

(f) What percent of values are outside the interval (101, 249)?

(g) What percent of values are outside the interval (64, 286)?

User Pork Chop
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1 Answer

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Final answer:

To draw a normal curve and label standard deviations, use the empirical rule. Percentages of values within and outside specific intervals can be calculated using the rule as well.

Step-by-step explanation:

(a) To draw a normal curve and label 1, 2, and 3 standard deviations on both sides of the mean, you can use the empirical rule. The empirical rule states that approximately 68% of values fall within 1 standard deviation, 95% fall within 2 standard deviations, and 99.7% fall within 3 standard deviations of the mean. So, for a normal distribution with a mean of 175 and a standard deviation of 37, you can calculate the values as follows:

1 standard deviation: Mean ± (1 * Standard Deviation) = 175 ± (1 * 37) = 138, 212

2 standard deviations: Mean ± (2 * Standard Deviation) = 175 ± (2 * 37) = 101, 249

3 standard deviations: Mean ± (3 * Standard Deviation) = 175 ± (3 * 37) = 64, 286

(b) To find the percentage of values within the interval (138, 212), you can use the empirical rule. Since this interval represents 1 standard deviation from the mean, approximately 68% of values fall within this range.

(c) To find the percentage of values within the interval (101, 249), you can again use the empirical rule. This interval represents 2 standard deviations from the mean, so approximately 95% of values fall within this range.

(d) Similarly, to find the percentage of values within the interval (64, 286), you can use the empirical rule. This interval represents 3 standard deviations from the mean, so approximately 99.7% of values fall within this range.

(e) To find the percentage of values outside the interval (138, 212), you can subtract the percentage within the interval from 100%. From part (b), we know that approximately 68% of values fall within 1 standard deviation of the mean, so approximately 32% of values fall outside this range.

(f) For the interval (101, 249), approximately 95% of values fall within 2 standard deviations of the mean. So, the percentage of values outside this interval is approximately 100% - 95% = 5%.

(g) Similarly, for the interval (64, 286), approximately 99.7% of values fall within 3 standard deviations of the mean. So, the percentage of values outside this interval is approximately 100% - 99.7% = 0.3%.

User Onur Turhan
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