Question

Kyle’s doctor told him that the z-score for his systolic blood pressure is 1.75. Which of the following is the best interpretation of this standardized score? The systolic blood pressure (given in millimeters) of males has an approximately normal distribution with mean µ = 125 and standard deviation σ = 14. If X = a systolic blood pressure score then X ~ N (125, 14).

a. Which answer(s) is/are correct?
1. Kyle's systolic blood pressure is 175.
2. Kyle's systolic blood pressure is 1.75 times the average blood pressure of men his age.
3. Kyle's systolic blood pressure is 1.75 above the average systolic blood pressure of men his age.
4. Kyles's systolic blood pressure is 1.75 standard deviations above the average systolic blood pressure for men.

b. Calculate Kyle's blood pressure.

Answer 1

a. 4. Kyles's systolic blood pressure is 1.75 standard deviations above the average systolic blood pressure for men.

b. His blood pressure is of 149.5 millimeters

Explanation:

Normal Probability Distribution:

Problems of normal distributions can be solved using the z-score formula.

In a set with mean
`\mu` and standard deviation
`\sigma`, the z-score of a measure X is given by:

`Z = (X - \mu)/(\sigma)`

The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.

a. Which answer(s) is/are correct?

His blood pressure has a zscore of 1.75, which means that it is 1.75 standard deviation above the mean value. So the correct answer is given by option 4.

b. Calculate Kyle's blood pressure.

We have to find X when
`Z = 1.75, \mu = 125, \sigma = 14`. So

`Z = (X - \mu)/(\sigma)`

`1.75 = (X - 125)/(14)`

`X - 125 = 1.75*14`

`X = 149.5`

His blood pressure is of 149.5 millimeters