Question

Count	Android User Id	Price Willing to Pay
1	976	850
2	890	1150
3	1	750
4	23	650
5	35	450
6	87	400
7	773	750
8	345	900
9	667	750
10	658	1050
11	894	900
12	420	850
13	900	950
14	921	850
15	122	700
16	144	950
17	156	1150
18	873	850
19	855	900
20	621	1150
21	9	1000
22	7	850
23	55	800
24	67	800
25	42	850

Part II: To study Android users you collect data on 25 randomly chosen people. See attached data file

d) Compute sample mean and sample standard deviation for Android users

e) Compute 5-number summary for Android users

f) Find the 95% confidence interval for the average phone price that an Android user willing to pay. How do you interpret it?

Answer 1

Solution:

From given data, we have descriptive statistics for the variable price willing to pay given as below:

Price Willing to Pay
Mean	850
Standard Error	36.96845502
Median	850
Mode	850
Standard Deviation	184.8422751
Sample Variance	34166.66667
Kurtosis	0.970603796
Skewness	-0.537846415
Range	750
Minimum	400
Maximum	1150
Sum	21250
Count	25

(Above descriptive statistics are calculated by using excel.)

d) Compute sample mean and sample standard deviation for Android users

Sample mean = Xbar = 850

Sample standard deviation = S = 184.8422751

e) Compute 5-number summary for Android users

A Five-Number Summary for the given data for price willing to pay is given as below:

Five-Number Summary
Minimum	400
First Quartile = Q1	750
Median = Q2	850
Third Quartile = Q3	950
Maximum	1150

(Calculated by using Excel)

f) Find the 95% confidence interval for the average phone price that an Android user willing to pay. How do you interpret it?

Confidence interval = Xbar ± t*S/sqrt(n)

From given data, we have

Sample mean = Xbar = 850

Sample standard deviation = S = 184.8422751

Sample size = n = 25

Confidence level = 95%

Degrees of freedom = df = n – 1 = 25 – 1 = 24

Critical t value = 2.0639 (by using t-table)

Confidence interval = 850 ± 2.0639*184.8422751/sqrt(25)

Confidence interval = 850 ± 2.0639*184.8422751/5

Confidence interval = 850 ± 2.0639* 36.96845502

Confidence interval = 850 ± 76.2991

Lower limit = 850 - 76.2991 = 773.70

Upper limit = 850 + 76.2991 = 926.30

WE are 95% confident that the average phone price that an Android user willing to pay will lies between 773.70 and 926.30.