statistic question

Using the data in BELOW find the 99% confidence interval for the variance AND standard deviation of the ages of the babies born at this particular hospital this year. 

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The data shown below represents the ages in months of 25 babies born at a particular hospital this year. Babies who are less than a month old are given an age of 0 months.

0	9	2	3	10
0	11	1	3	1
2	8	4	7	1
4	7	6	6	1
5	6	7	8	4

 Find the 95% confidence interval for the mean age of the babies born at this particular hospital this year.

The mean (average) X is given calculated as 

X = Sum of all the ages of babies / Number of babies

X = 116/25

X = 4.64 months

Standard Deviation = SD = 3.2259

The degree of freedom = d.f. = n – 1 = 24

 

The t value is t_α/2 = t_0.025 = 2.0639

The 95% confidence interval is given as

X +/- t_α/2 S/n  

4.64 +/- ((2.0639*3.2259)/25)