Question

How many commuters must be randomly selected to estimate the mean driving time of Chicago commuters? We want 95% confidence that the sample mean is within 3 minutes of the population mean, and the population standard deviation is known to be 12 minutes.

Answer 1

Answer:

61 commuters must be randomly selected to estimate the mean driving time of Chicago commuters.  

Step-by-step explanation:

Answer 2

Answer:

61 commuters must be randomly selected to estimate the mean driving time of Chicago commuters.                

Step-by-step explanation:

Given : We want 95% confidence that the sample mean is within 3 minutes of the population mean, and the population standard deviation is known to be 12 minutes.

To find : How many commuters must be randomly selected to estimate the mean driving time of Chicago commuters?

Solution :

At 95% confidence the z-value is z=1.96

The sample mean is within 3 minutes of the population mean i.e. margin of error is E=3 minutes

The population standard deviation is s=12 minutes

n is the number of sample

The formula of margin of error is given by,

$E=\frac{s\times z}{\sqrt{n}}$

Substitute the value in the formula,

$3=\frac{12\times 1.96}{\sqrt{n}}$

$3=\frac{23.52}{\sqrt{n}}$

$\sqrt{n}=\frac{23.52}{3}$

$\sqrt{n}=7.84$

Squaring both side,

$n=61.4656$

Therefore, 61 commuters must be randomly selected to estimate the mean driving time of Chicago commuters.