1. Use the mean and the standard deviation obtained from the last module and test the claim that the mean age of all books in the library is greater than 2005.

My module:

I use the method of stratified random sampling to collect the sample of books. I randomly select 4 types of books namely friction, cooking, historical, and love stories. My strata is the type of book. From each of these book types (strata), I randomly select 10 books. I expect no biases in the data, as my sample is a good representative of the population.

I take the level of significance Alpha as 5%. this indicates I am 95% confident about my results. The data obtained from the library regarding the age of the book is given below.

Data:

1

13

10

13

2

13

8

13

8

6

10

10

15

11

11

2

15

11

9

9

6

1

10

11

2

2

11

3

10

10

10

8

12

1

15

6

9

2

7

4

Descriptive statistics is:

Mean=	8.25	AVGERAGE
sd= sqrt(var)	4.29	STDEV
n=	40.00	COUNT
alpha=	0.05

The confidence interval is given by:

Z(a/2) z(0.05/2) 1.960

CI = mean +-z(a/2,n-1)*(sd/sqrt(n)) lower = 8.25-1.96*(4.28922322774601/sqrt(40))= 6.92 upper = 8.25 + 1.96*(4.28922322774601/sqrt(40))= 9.58

This indicates that I am 95% confident that the estimated population mean age of books lies in the interval [6.92, 9.58] years.