Workshop # 1
1305AFE
Group-W112
Date: 05-03-2018
Time: 4.00pm-4.50 pm
Venue: N53_0.64
Tutor: Chandika Gunasinghe
The importance of workshop 1
• By answering for the questions in this workshop, you will be able to further
develop your understanding on;
 the difference between a population and a sample (Q1.3 and 1.4)
the difference between a population parameter and a sample statistic (Q1.3 and 1.4)
the types of data (numerical, nominal, and ordinal) (Q2.4 and 2.8)
the methods of collecting data (Q2.15 and 2.16)
 the points needed to consider when designing a questionnaire (Q2.17)
 the sources of errors between the target population and the sampled population (Q2.18)
 sampling plans (simple random sampling, stratified random sampling and cluster sampling)
(Q2.21, 2.22 and 2.23).
Q1.3. The manager of a bank with 12000 customers commissions a survey to
gauge customer views on internet banking, which would incur lower bank fees.
In the survey, 21% of the 300 customers interviewed said they are interested in
internet banking.
a. What is the population of interest?
Answer: Views on internet banking of the 12 000 customers.
a. What is the sample?
Answer: Views on internet banking of the 300 customers surveyed.
a. Is the value 21% a parameter or a statistic?
Answer: Statistic
Q1.4. A light bulb manufacturer claims that less than 5% of his bulbs are defective. When 1000
bulbs were drawn from a large production run, 1% were found to be defective.
a. What is the population of interest?
Answer: complete production run of light bulbs
b. What is the sample?
Answer: 1000 bulbs selected
c. What is the parameter?
Answer: the proportion of the light bulbs that are defective in the whole production run
d. What is the statistic?
Answer: the proportion of the light bulbs that are defective in the sample of 1000 bulbs selected
e. Does the value 5% refer to the parameter or to the statistic?
Answer: parameter
f. Is the value 1% a parameter or statistic
Answer: statistic
g. Explain briefly how the statistic can be used to make inferences about the parameter to test the claim.
Answer: Because the sample proportion (1%) is much less than the claimed 5% (or population proportion), we
can conclude with confidence that there is evidence to support the claim.
Q2.4. Information concerning a magazine’s readership is of interest both to the publisher and to
the magazine’s advertisers. A survey of 500 subscribers included the following questions. For
each question, determine the data type of possible responses?
a. What is your age?
Answer: numerical
b. What is your gender?
Answer: nominal
c. What is your marital status?
Answer: nominal
d. Is your annual income less than $30,000, between $ 30,000 and $ 60,000 or above $ 60,000?
Answer: ordinal
e. To how many other magazines do you subscribe?
Answer: numerical
f. How do you rate the future article published in the current issue of the magazine (very good, good, or
poor)
Answer: ordinal
Q2.8. Residents of a high-rise block of flats in Perth city were recently surveyed
and asked a series of questions. Identify the type of data for each question.
a. What is your age?
Answer: numerical
b. On which floor do you live?
Answer: ordinal
c. Do you own or rent?
Answer: nominal
d. How many bed rooms are there in your flat?
Answer: numerical
e. Does your block have a pool?
Answer: nominal
f. How would you rate your satisfaction with the common facilities (e.g. swimming pool, tennis
court) available to the residents (very good, good, or poor)
Answer: ordinal
Q2.15.
a. Briefly describe how you might design a study to investigate the relationship between smoking
and lung cancer?
Answer:
b. Is your study from part (a) is observational or experimental? Explain why?
Answer:
Q2.16.
a. List three methods of conducting a survey of people?
Answer:
 a personal interview
 a telephone interview
 a self-administered questionnaire
b. Give an important advantage and disadvantage of each of the methods listed in part (a)?
Advantage
Disadvantage
Answer: Survey method
Personal interview
 A higher response rate
 Expensive because the need to
 Fewer incorrect responses
higher well trained interviewers
arising from respondents
and possibly pay travel related
misunderstanding of
cost if the survey is conducted
some questions
over a large geographical area
Telephone interview
Self-administered
questionnaire
 Less expensive
 Least expensive
 Lower response rate
 Lower response rates and less
accuracy than personal interviews
Q2.17. List five important points to consider when designing a
questionnaire?
• (i). The questionnaire should be short
• (ii). Questions should be clearly worded and unambiguous
• (iii). Consider using the dichotomous or multiple-choice questions, but
take care that respondents needn’t make unspecified assumptions before
answering the questions.
• (iv). Avoid using leading questions. e.g. “Do you think that tuition fees
make students less keen to go to university?”
• (v). When preparing the questions, think about how you tabulate and
analyse the responses.
Q2.18. For each of the following sampling plans, indicate why the
target population and the sampled population are not the same.
(a). In order to determine the opinions and attitudes of customers who regularly shop at a
particular centre, a surveyor stands outside a large department store in the centre and
randomly selects people to participate in the survey.
[Target population in (a) is all the customers who regularly shop at the mall.
Sampled population is the randomly selected customers who shop at a large department
store in the centre]
Answer:
The sampled population will exclude both;
those who avoid large department stores in favour of smaller shops and
those who consider their time too valuable to spend participating in a survey
Q2.18. For each of the following sampling plans, indicate why the
target population and the sampled population are not the same.
(b). A library wishes to estimate the proportion of its books that have been
damaged. They decide to select one book per shelf as a sample, by
measuring 30 cm from the left edge of each shelf and selecting the book in
that location.
[Target population in (b) is the proportion of all the books that have been
damaged . Sampled population is the proportion of books randomly selected
from each self]
Answer:
The sampled proportion will contain a disproportionate number of thick
books, because of the manner in which the sample is selected.
Q2.18. For each of the following sampling plans, indicate why the
target population and the sampled population are not the same.
(c). A political surveyor visits 200 residences and asks the eligible voters
present in the house at the time when they intend to vote for. The visits take
place during the afternoons.
[Target population in (c) is the all eligible voters. Sampled population is the
eligible voters who are at home in the afternoon]
Answer:
The sample population consists of those eligible voters who are at home in
the afternoon, thereby excluding most of those with full-time jobs (or at
schools).
Q2.21. The operations manager of a large plant with four
departments wants to estimate the employee working hours lost per
month due to accidents. Describe a sampling plan that would be
suitable for estimating the plant-wide loss and for comparing
departments.
Answer:
The operations manager can select stratified random samples where the
strata are the four departments. Simple random sampling can be conducted
in each department.
Q2.22. A large university campus has 60,000 students. The president of students’
association wants to conduct a survey of the students to determine their views on an
increase in the student activity fee. She would like to acquire information about all
the students but would also like to compare the school of business, the faculty of
arts and sciences, and the graduate school. Describe a sampling plan that
accomplishes these goals.
Answer:
Stratified random sampling is recommended. The strata are;
1. the school of business
2. the faculty of arts
3. the graduate school and
4. the all the other schools and faculties
The data can be used to acquire information about the entire campus but also
compare the four strata.
Q2.23.A telemarketing firm has recorded a list of the households that have
purchased one or more of the company’s products. These data number in the
millions. They would like to conduct a survey of purchasers to obtain information
about their attitude concerning the timing of the telephone calls. The president of
the company would like to compare the attitudes of people in the west, south, north,
and east. Describe a suitable sampling plan.
Answer:
A stratified random sampling plan accomplishes the president’s goals. The strata
are the four areas; the west, south, north, and east.
This will enable the statistics practitioner to learn about the entire population and
to compare four areas.