Question

From a random sample of 58 businesses, it is found that the mean time the owner spends on administrative issues each week is 21.69 with a population standard deviation of 3.23. What is the 95% confidence interval for the amount of time spent on administrative issues?

Answer 1

Answer: (20.86, 22.52)

Step-by-step explanation:

Formula to find the confidence interval for population mean :-

$\overline{x}\pm z^*\dfrac{\sigma}{\sqrt{n}}$

, where $\overline{x}$ = sample mean.

z*= critical z-value

n= sample size.

$\sigma$ = Population standard deviation.

By considering the given question , we have

$\overline{x}= 21.69$

$\sigma=3.23$

n= 58

Using z-table, the critical z-value for 95% confidence = z* = 1.96

Then, 95% confidence interval for the amount of time spent on administrative issues will be :

$21.69\pm (1.96)\dfrac{3.23}{\sqrt{58}}$

$=21.69\pm (1.96)\dfrac{1.7}{7.61577}$

$=21.69\pm (1.96)(0.223221)$

$\approx21.69\pm0.83$

$=(21.69-0.83,\ 21.69+0.83)=(20.86,\ 22.52)$

Hence, the 95% confidence interval for the amount of time spent on administrative issues = (20.86, 22.52)