THE INTERNATIONAL UNIVERSITY (IU) Course: Statistics for Business
Department of Business Administration FINAL EXAMINATION INDEX 1 STATISTICS FOR BUSINESS Duration: 120 minutes
Dean of School of Business Lecturers: Student ID: Date: September 1st, 2020 Name: Dr. Hồ Nhựt Quang Dr. Phan Nguyen KyPhuc INSTRUCTIONS: 1.
This is an opened book examination. 2.
Calculator and Laptops are allowed. Total pages: 02 (including this page) WRITTEN QUESTIONS (100%)
Question 1: (15pts) The shelf life of a carbonated beverage is of interest. Ten bottles are randomly
selected and tested, and the following results are obtained: 108 124 124 106 115 138 163 159 134 139
a) We would like to demonstrate that the mean shelf life exceeds 120 days. Set up appropriate hypotheses for investigating this claim.
b) Find the P-value for the test in above question
c) If the significant level 𝛼 = 0.01. What are your conclusions? 
Question 2: (15pts) In semiconductor manufacturing wet chemical etching is often used to remove silicon
from the backs of wafers prior to metalization. The etch rate is an important characteristic of this process.
Two different etching solutions are being evaluated. Eight randomly selected wafers have been etched in
each solution, and the observed etch rates (in mils/min) are as follows Solution 1 9.9 9.4 10.0 10.3 10.6 10.3 9.3 9.8 Solution 2 10.2 10.0 10.7 10.5 10.6 10.2 10.4 10.3
a) Do the data indicate that the claim that both solutions have the same mean etch rate is valid? Use 𝛼 =
0.05 and assume equal variances. 
b) Find a 95 percent confidence interval on the difference in mean etch rates. 
Statistics for Business – Final Exam
THE INTERNATIONAL UNIVERSITY (IU) Course: Statistics for Business
Department of Business Administration
Question 3: (15pts) Ten pigs are given a test to check whether the new drugs affect their weights. The
data collected before and after the drug usage are as follows: Patient 1 2 3 4 5 6 7 8 9 10 Before 100 104 98 102 105 103 99 101 102 105 After 110 112 100 99 115 109 115 110 107 112
Do the data indicate this drug changes the pigs’ weight at α = 0.05? (15pts)
Question 4: (15pts) The deflection temperature under load for two different formulations of ABS plastic
pipe is being studied. Two samples of 12 observations each are prepared using each formulation and the
deflection temperatures (in °F) are reported below:
Make the proper hypothesis test that two formulation have equal variance? 
Question 5: (20 pts) Four different designs for a digital computer circuit are being studied to compare the
amount of noise present. The following data have been obtained: Des. 1 Des. 2 Des. 3 Des. 4 19 80 47 95 20 61 26 46 19 73 25 83 30 56 35 78 8 80 50 97
Is the same amount of noise present for all four designs? Use α = 0.05
Question 6: (20pts) :A study was performed on wear of a bearing y and its relationship to x oil viscosity 1
and x2 load. The following data were obtained:
Fit a multiple linear regression equation to the following data set at α = Write down the equation 0.05.
Conduct the proper test to see if some inputs can be excluded at α = 0.05
Statistics for Business Final Exam –