Question

For a data set of the pulse rates for a sample of adult​ females, the lowest pulse rate is 39 beats per​ minute, the mean of the listed pulse rates is x=76.0 beats per​ minute, and their standard deviation is s=13.8 beats per minute. a. What is the difference between the pulse rate of 39 beats per minute and the mean pulse rate of the​ females? b. How many standard deviations is that​ [the difference found in part​ (a)]? c. Convert the pulse rate of 39 beats per minutes to a z score. d. If we consider pulse rates that convert to z scores between −2 and 2 to be neither significantly low nor significantly​ high, is the pulse rate of 39 beats per minute​ significant

Answer 1

a) The difference is of -37, that is, this pulse rate is 37 beats per minute below the mean.

b) 2.68 standard deviations below the mean.

c) Z = -2.68.

d) Z-score below -2, so a pulse rate of 39 beats per minute is significantly low.

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. What is the difference between the pulse rate of 39 beats per minute and the mean pulse rate of the​ females?

Difference between 39 and 76, so 39 - 76 = -37.

The difference is of -37, that is, this pulse rate is 37 beats per minute below the mean.

b. How many standard deviations is that​ [the difference found in part​ (a)]

Standard deviation of 13.8, so:

-37/13.8 = -2.68

So 2.68 standard deviations below the mean.

c. Convert the pulse rate of 39 beats per minutes to a z score.

2.68 standard deviations below the mean, so Z = -2.68.

d. If we consider pulse rates that convert to z scores between −2 and 2 to be neither significantly low nor significantly​ high, is the pulse rate of 39 beats per minute​ significant?

Z-score below -2, so a pulse rate of 39 beats per minute is significantly low.