Question

In a​ study, researchers compared the variability in product of a particular piece of equipment to a known analytic capability to decide whether product consistency could be improved. The following data were obtained for 10 batches of product. Preliminary test results suggest the data are normally distributed and that s=0.558. Construct a 980% confidence interval for the process variation of the piece of equipment under consideration.

29.7

28.6

29.7

30.1

29.2

29.4

29.2

28.9

30.5

29.4

The 90% confidence interval is from _ to _.

​(Round to three decimal places as​ needed.)

Answer 1

From the sample data : n=10 ,

The sample mean is ,

Now , df=degrees of freedom=n-1=10-1=9

The critical value is ,

; From t-table

Therefor , the 90% confidence interval is ,

Therefore , the 90% confidence interval is from 29.147 to 29.793