lOMoARcPSD| 47389193
UNIVERSITY EXAMINATIONS
Jan/Febr 2025
STA4820
Statistical Techniques for Science and Engineering
100 Marks
Duration: 3 Hours
EXAMINERS:
FIRST: Ms B Tabo
SECOND: Prof LK Debusho
EXTERNAL: Prof F Habyarimana (UKZN)
________________________________________________________________________
This paper consists of 14 pages.
INSTRUCTIONS
1. This is an open book examination. You may use your textbook, your course material
or any other printed material to answer the questions.
2. You must upload your answers in one PDF file.
3. Answer all the questions.
4. Show all the intermediate steps in order to get partial marks.
5. A zero mark will be awarded for a correct answer without intermediate steps!
6. A zero mark will be awarded for copied answers from other persons/students!
, lOMoARcPSD| 47389193
2 STA4820
JAN/FEBR 2025
ADDITIONAL STUDENT INSTRUCTIONS
1. Students must upload their answer scripts in a single PDF file on the official
myExams platform (answer scripts must not be password protected or uploaded as
"read-only" files).
2. NO e-mailed scripts will be accepted.
3. Students are advised to preview submissions (answer scripts) to ensure legibility and
that the correct answer script file has been uploaded.
4. Students are permitted to resubmit their answer scripts should their initial submission
be unsatisfactory.
5. Incorrect file format and uncollated answer scripts will not be considered.
6. Incorrect answer scripts and/or submissions made on unofficial examination
platforms (including the invigilator cell phone application) will not be marked and no
opportunity will be granted for resubmission.
7. A mark awarded for an incomplete submission will be the student's final mark. No
opportunity for resubmission will be granted.
8. A mark awarded for illegible scanned submission will be the student's final mark. No
opportunity for resubmission will be granted.
9. Only the last file uploaded and submitted will be marked.
10. Submissions will only be accepted from registered student accounts.
11. Students who have not utilised invigilation or proctoring tools will be deemed to have
transgressed Unisa's examination rules and will have their marks withheld.
12. Students must complete the online declaration of their work when submitting.
Students suspected of dishonest conduct during the examinations will be subjected
to disciplinary processes. Students may not communicate with other students or
request assistance from other students during examinations. Plagiarism is a violation
of academic integrity, and students who do plagiarise or copy verbatim from
published work will be in violation of the Policy on Academic Integrity and the Student
Disciplinary Code and may be referred to a disciplinary hearing. Unisa has zero
tolerance for plagiarism and/or any other forms of academic dishonesty.
13. Students are provided 30 minutes to submit their answer scripts after the official
examination time. Students who experience technical challenges should report to the
SCSC on 080 000 1870 or their College exam support centres (refer to the Get help
during the examinations by contacting the Student Communication Service Centre
(unisa.ac.za)) within 30 minutes. Queries received after one hour of the official
examination duration time will not be responded to. Submissions made after the
, lOMoARcPSD| 47389193
3 STA4820
JAN/FEBR 2025
official examination time will be rejected by the examination regulations and will not
be marked.
14. Non-adherence to the processes for uploading examination responses will not qualify
the student for any special concessions or future assessments.
15. Queries that are beyond Unisa's control include the following:
a. Personal network or service provider issues
b. Load shedding/limited space on personal computer
c. Crashed computer
d. Using work computers that block access to myExams site (work firewall challenges)
e. Unlicensed software (e.g. license expires during exams)
Postgraduate students experiencing the above challenges are advised to apply for an
aegrotat and submit supporting evidence within ten days of the examination session.
Students will not be able to apply for an aegrotat for a third examination opportunity.
Postgraduate/Undergraduate students experiencing the above challenges in their
second examination opportunity will have to reregister for the affected module.
16. Students experiencing technical challenges should contact the SCSC on 080 000
1870 or via e-mail at or refer to the Get help during the
examinations by contacting the Student Communication Service Centre (unisa.ac.za)
for the list of additional contact numbers. Communication received from your myLife
account will be considered.
, lOMoARcPSD|47389193
4 STA4820
JAN/FEBR 2025
QUESTION 1 [15]
Spam is the price we pay for being able to easily communicate by e-mail. Does spam affect
everyone equally? In a preliminary study, university professors, administrators, and students
were randomly sampled. Each person was asked to count the number of spam messages
received that day. The statistics follow:
Table 1
University community
Statistic Professors Administrators Students
끫뢶 5 5 5
끫룊̅ 6,4 10,4 10,8
끫룀 2 48,3 16,3 37,7
a) Using the above statistics, construct and complete a one-way ANOVA table. (9)
b) Can we infer at 끫뷸 = 0.05 significance level that there are differences in age between
the computer brands? Substantiate your conclusions by giving clear calculations. (6)
QUESTION 2 [12]
The operations manager of a company that manufactures shirts wants to determine
whether there are differences in the quality of workmanship among the three daily shifts.
She randomly selects 600 recently made shirts and carefully inspects them. Each shirt is
classified as either perfect or flawed, and the shift that produced it is also recorded. The
accompanying cross-classification table summarizes the number of shirts that fell into
each cell. Do these data provide sufficient evidence to infer that there are differences in
quality between the three shifts? Elaborate and give clear calculations.
[TURN OVER]
Downloaded by Dorothy Reyes ()
UNIVERSITY EXAMINATIONS
Jan/Febr 2025
STA4820
Statistical Techniques for Science and Engineering
100 Marks
Duration: 3 Hours
EXAMINERS:
FIRST: Ms B Tabo
SECOND: Prof LK Debusho
EXTERNAL: Prof F Habyarimana (UKZN)
________________________________________________________________________
This paper consists of 14 pages.
INSTRUCTIONS
1. This is an open book examination. You may use your textbook, your course material
or any other printed material to answer the questions.
2. You must upload your answers in one PDF file.
3. Answer all the questions.
4. Show all the intermediate steps in order to get partial marks.
5. A zero mark will be awarded for a correct answer without intermediate steps!
6. A zero mark will be awarded for copied answers from other persons/students!
, lOMoARcPSD| 47389193
2 STA4820
JAN/FEBR 2025
ADDITIONAL STUDENT INSTRUCTIONS
1. Students must upload their answer scripts in a single PDF file on the official
myExams platform (answer scripts must not be password protected or uploaded as
"read-only" files).
2. NO e-mailed scripts will be accepted.
3. Students are advised to preview submissions (answer scripts) to ensure legibility and
that the correct answer script file has been uploaded.
4. Students are permitted to resubmit their answer scripts should their initial submission
be unsatisfactory.
5. Incorrect file format and uncollated answer scripts will not be considered.
6. Incorrect answer scripts and/or submissions made on unofficial examination
platforms (including the invigilator cell phone application) will not be marked and no
opportunity will be granted for resubmission.
7. A mark awarded for an incomplete submission will be the student's final mark. No
opportunity for resubmission will be granted.
8. A mark awarded for illegible scanned submission will be the student's final mark. No
opportunity for resubmission will be granted.
9. Only the last file uploaded and submitted will be marked.
10. Submissions will only be accepted from registered student accounts.
11. Students who have not utilised invigilation or proctoring tools will be deemed to have
transgressed Unisa's examination rules and will have their marks withheld.
12. Students must complete the online declaration of their work when submitting.
Students suspected of dishonest conduct during the examinations will be subjected
to disciplinary processes. Students may not communicate with other students or
request assistance from other students during examinations. Plagiarism is a violation
of academic integrity, and students who do plagiarise or copy verbatim from
published work will be in violation of the Policy on Academic Integrity and the Student
Disciplinary Code and may be referred to a disciplinary hearing. Unisa has zero
tolerance for plagiarism and/or any other forms of academic dishonesty.
13. Students are provided 30 minutes to submit their answer scripts after the official
examination time. Students who experience technical challenges should report to the
SCSC on 080 000 1870 or their College exam support centres (refer to the Get help
during the examinations by contacting the Student Communication Service Centre
(unisa.ac.za)) within 30 minutes. Queries received after one hour of the official
examination duration time will not be responded to. Submissions made after the
, lOMoARcPSD| 47389193
3 STA4820
JAN/FEBR 2025
official examination time will be rejected by the examination regulations and will not
be marked.
14. Non-adherence to the processes for uploading examination responses will not qualify
the student for any special concessions or future assessments.
15. Queries that are beyond Unisa's control include the following:
a. Personal network or service provider issues
b. Load shedding/limited space on personal computer
c. Crashed computer
d. Using work computers that block access to myExams site (work firewall challenges)
e. Unlicensed software (e.g. license expires during exams)
Postgraduate students experiencing the above challenges are advised to apply for an
aegrotat and submit supporting evidence within ten days of the examination session.
Students will not be able to apply for an aegrotat for a third examination opportunity.
Postgraduate/Undergraduate students experiencing the above challenges in their
second examination opportunity will have to reregister for the affected module.
16. Students experiencing technical challenges should contact the SCSC on 080 000
1870 or via e-mail at or refer to the Get help during the
examinations by contacting the Student Communication Service Centre (unisa.ac.za)
for the list of additional contact numbers. Communication received from your myLife
account will be considered.
, lOMoARcPSD|47389193
4 STA4820
JAN/FEBR 2025
QUESTION 1 [15]
Spam is the price we pay for being able to easily communicate by e-mail. Does spam affect
everyone equally? In a preliminary study, university professors, administrators, and students
were randomly sampled. Each person was asked to count the number of spam messages
received that day. The statistics follow:
Table 1
University community
Statistic Professors Administrators Students
끫뢶 5 5 5
끫룊̅ 6,4 10,4 10,8
끫룀 2 48,3 16,3 37,7
a) Using the above statistics, construct and complete a one-way ANOVA table. (9)
b) Can we infer at 끫뷸 = 0.05 significance level that there are differences in age between
the computer brands? Substantiate your conclusions by giving clear calculations. (6)
QUESTION 2 [12]
The operations manager of a company that manufactures shirts wants to determine
whether there are differences in the quality of workmanship among the three daily shifts.
She randomly selects 600 recently made shirts and carefully inspects them. Each shirt is
classified as either perfect or flawed, and the shift that produced it is also recorded. The
accompanying cross-classification table summarizes the number of shirts that fell into
each cell. Do these data provide sufficient evidence to infer that there are differences in
quality between the three shifts? Elaborate and give clear calculations.
[TURN OVER]
Downloaded by Dorothy Reyes ()
