Question

Using the accompanying Accounting Professionals data to answer the following questions. a. Find and interpret a 95​% confidence interval for the mean years of service. b. Find and interpret a 95​% confidence interval for the proportion of employees who have a graduate degree.

Employee	Years of Service	Graduate Degree?
1	5	N
2	10	N
3	8	Y
4	14	Y
5	8	Y
6	7	Y
7	20	N
8	6	N
9	9	Y
10	19	Y
11	10	N
12	28	N
13	9	N
14	8	N
15	8	Y
16	5	N
17	31	N
18	9	N
19	8	N
20	26	Y

Answer 1

Using Excel

a)

mean	12.4000
sd	7.9498
n	20

95% confidence interval

(Xbar +- t * s/sqrt(n))

df =n-1 = 19

alpha = 0.05

t = t.inv.2t(alpha,df)

t	2.093
t * sd/sqrt(n)	3.721
lower	8.6794
upper	16.1206

b)

Employee	Years of Service	Graduate Degree?
3	8	Y
4	14	Y
5	8	Y
6	7	Y
9	9	Y
10	19	Y
15	8	Y
20	26	Y

X = 8

n = 20

(p^ +- z *sqrt(p^(1-p^)/n)

p^ = X/n

z = 1.96 for 95%

p^

0.400

E = z *sqrt(p^(1-p^)/n)

2-tailed	1.9600
E	0.2147
lower	0.1853
upper	0.6147