Question

1)Suppose that a random sample of 144 graduate-admissions personnel was asked what role scores on standardized tests play in consideration of a candidate for graduate school. Of these sample members, 79 answered "very important." Find a 95% confidence interval for the population proportion of graduate admissions personnel with this view.

2) A manufacturer bonds a plastic coating to a metal surface. A random sample of nine observations on the thickness of this coating is taken from a week's output and the thickness (in millimeters) of these observations are shown below. Assuming normality, find a 90% confidence interval for the population variance.

19.1.

21.7

18.7

20.1

21.5

19.5

19.1

20.2

20.3

please explain step by step and which table u have used and how u get to the result.

Answer 1