Question

A study of 40 white mice

Answer 1

Answer:

$3.20-1.304\frac{0.8}{\sqrt{40}}=3.035$    

$3.20+1.304\frac{0.8}{\sqrt{40}}=3.365$    

And the confidence interval would be between (3.035;3.365)    

Step-by-step explanation:

Information given

$\bar X=3.20$ represent the sample mean

$\mu$ population mean (variable of interest)

s=0.8  represent the sample standard deviation

n=40 represent the sample size  

Confidence interval

The confidence interval for the mean is given by the following formula:

$\bar X \pm t_{\alpha/2}\frac{s}{\sqrt{n}}$   (1)

The degrees of freedom are given by:

$df=n-1=40-1=39$

The Confidence level is 0.80 or 80%, the significance  would be $\alpha=0.2$ and $\alpha/2 =0.1$, and the critical value would be $t_{\alpha/2}=1.304$

Now we have everything in order to replace into formula (1):

$3.20-1.304\frac{0.8}{\sqrt{40}}=3.035$    

$3.20+1.304\frac{0.8}{\sqrt{40}}=3.365$    

And the confidence interval would be between (3.035;3.365)