Question

Chapter 3 Statistics

A certain group of test had pulse rates with a mean of 73.8 beats per minute and a standard deviation of 10.8 beats per minute. Would it be unusual for one of the test subjects to have a pulse rate of 45.4 beats per minute?

a) What is the minimum "usual" value?

b) What is the maximum "usual" value?

c) Is 45.4 beats per minute an unusual pulse rate? Explain.

Answer 1

This is a normal distribution question with

a) Given in the question

P(X < x) = 0.05

This implies that

P(Z < -1.6448) = 0.05

With the help of formula for z, we can say that

x = 56.0356

b) Given in the question

P(X < x) = 0.95

This implies that

P(Z < 1.64485) = 0.95

With the help of formula for z, we can say that

x = 91.5644

c) x = 45.4

P(x < 45.4)=?

The z-score at x = 45.4 is,

z = -2.6296

This implies that

P(x < 45.4) = P(z < -2.6296) = {0.0042

It is unusual value

PS: you have to refer z score table to find the final probabilities.

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