The recipe for producing a highquality cement specifies that

The recipe for producing a high-quality cement specifies that the required percentage of SiO2 is 6.2%. A quality control engineer evaluates this specification weekly by randomly selecting samples from r on a daily basis. On a given day, she obtained the following values: 1.70 9.86 5.44 4.28 4.59 8.76 9.16 6.28 3.83 3.17 5.98 2.77 3.59 3.17 8.46 7.76 5.55 5.95 9.56 3.58 (a) Estimate the mean percentage of Si02 using a 95% confidence interval. (b) Evaluate whether the percentage of Si02 is different from the value specified in the recipe using an a There is not enough evidence to conclude that the mean percentage of SiO2 is different from 6.2%. There is enough evidence to conclude that the mean percentage of SiO2 is different from 6.2%. (c)Use the following plot to determine if the procedures you used in parts (a) and (b) were valid. This answer has not been graded yet.

Solution

The degree of freedom =n-1=20-1=19

It is a two-tailed test.

So the p-value =2*P(t with df=19<-0.941596) =0.3582 (from student t table)