Stats Help?

Question

For women aged 18-24, systolic bp (in mmHg) are normally distributed with a mean of 114.8 and a standard deviation of 13.1. Hypertension is commonly defined as systolic blood pressure above 140.

If 10 women aged 18-24 are randomly selected, what is the probability their mean systolic blood pressure is greater than 140?

Answer 1

First you must understand the terms.

The mean is: Their average. That is, adding them up and dividing by their number. So if there are 10 women, adding up all their BP's and dividing by 10 will equal 114.8

The standard deviation measures the spread of a set of data around the mean. So the mean is 114.8 the deviation is 13.1 more and 13.1 less. That means the lowest is 101.7 and the highest is 127.9

So the probability (the chance that something is likely to happen or be the case) of their mean BP being 140 is NIL

Answer 2

Menthoids was correct that first you need to understand the terms. Unfortunately, she does not understand what a standard deviation is.

Here is the way to find the answer:

120 - 114.8 = 5.2 mmHg

5.2 / 13.1 = 0.4 standard deviations

Using the table at

http://www.itl.nist.gov/div898/handbook/eda/section3/eda3671.htm

0.4 standard deviations = 15.5% of the population that will have a systolic BP between 114.8 and 120. Add 15.5% to the 50% that will have a systolic BP below 114.8 to get the answer that

there is a 65.5% that her systolic BP is below 120 mmHg.