Question

A medical stats class is interested in the mean pulse rate of "senior citizens". How many individuals are required to estimate the pulse rate with 99% confidence that the mean is within 2 beats per minute of the population mean. Based on 2000 NIH data, assume a std deviation of 12.5 beats per minute.

b) Recent data suggests the std deviation is closer to 17 bpm. How does a 99% CI with this std deviation compare to (a) above?

Answer 1

Solution :

Given that,

standard deviation =   =12.5

Margin of error = E = 2

At 99% confidence level the z is,

= 1 - 99%

= 1 - 0.99 = 0.01

/2 = 0.005

Z/2 = 2.576

sample size = n = [Z/2* / E] 2

n = ( 2.576* 12.5 /2 )2

n =259.21

Sample size = n =260

(B)

Solution :

Given that,

standard deviation =   =17

Margin of error = E = 2

At 99% confidence level the z is,

= 1 - 99%

= 1 - 0.99 = 0.01

/2 = 0.005

Z/2 = 2.576

sample size = n = [Z/2* / E] 2

n = ( 2.576* 17 /2 )2

n =479.43

Sample size = n =480