Question

Data on the blood cholesterol levels of 6 rats give mean = 85, s= 12. A 95% confidence interval for the mean blood cholesterol of rats under this condition is
a)72.4 to 97.6
b)73.0 to 97.0
c)75.4 to 94.6
d)72.4 to 94.6

Answer 1

The equation of this would be

$true \ mean=mean \ +/- \ z\frac{s}{ \sqrt{n} }$

The z-value for a 95% confidence level is equal to 1.96.

Then the lower limit would be:

$85-1.96 \frac{12}{ \sqrt{6} }=75.398$

And the higher limit would be:

$85+1.96 \frac{12}{ \sqrt{6} }=94.60$

Therefore, the answer is

c)75.4 to 94.6

I hope I was able to explain it clearly. Have a good day :)

Answer 2

The correct answer is:

c)75.4 to 94.6

Explanation:

The formula for a confidence interval is:

$\mu \pm z*(\frac{\sigma}{\sqrt{n}})$,

where μ is the mean, z is the z-score associated with the level of confidence we want, σ is the standard deviation, and n is the sample size.

Our mean is 85, our standard deviation is 12, our sample size is 6, and since we want 95% confidence, our z-score is 1.96:

$85\pm 1.96(\frac{12}{\sqrt{6}})=85\pm 9.6=85-9.6, 85+9.6=75.4, 94.6$