The University of the South Pacific
Tutorial 2 Data Collection- Sampling
EC203 Economic Statistics
Learning Outcomes

Key objective of sampling.

Different techniques of Probability (or Random) Sampling; including simple random, stratified, and cluster.

Issues involved in selection of sampling techniques i.e. strength and weakness of each method.

Application of these techniques in Economic Surveys/Business Surveys.

Errors in data collection.
Questions
1. Define and Differentiate between a census and a sample. And state advantages and disadvantages of
both methods of data collection.
2. How can we overcome disadvantages of sampling to a certain extent?
3. Discuss advantages of random sampling.
4. What are the important factors to be considered in choosing sampling techniques?
5. Tevita a newly graduated accountant from USP starts job at PWC as an external auditor. His first job
was to audit account receivables section of MH supermarket. MH has a total of 8500 debtors, who
have purchased goods on credit from MH. Out of these 8500 debtors, 3400 owes less than $5000. 4250
owes between $5000 - $20000 and 850 owes more than $20000. Tevita was requested to audit 500
accounts to ensure that account receivable balance is true and fair in the financial reports. The MH
supermarket accountant assisted Tevita by providing list of these debtors in order of amount owed
ranging from lowest to highest numbered from 0001 to 8500.
a) What is population of interest and sample size?
b) Using simple random sample state who will be the first five debtors to be selected.( Use
random Numbers Table provided below ,Select the sample starting at the first digit of row 2
and working along the row.)
Table 1: Random Numbers
7898 8002 4418 2747 8079 4993 6863 9542 0949 4531 6955 5826 9971 6233 7887
8640 3204 6906 5719 1116 5982 9532 2422 8333 8828 9002 2680 1928 8532 3600
4431 3453 3070 5239 3168 6490 0274 8443 9984 7503 0263 8086 3372 5454 1599
5868 4764 0158 1225 5558 7840 9394 8126 6974 1561 4765 0758 8717 6979 6306
8514 6959 7775 5844 5147 9173 4558 9107 0453 6119 2915 6586 9670 6580 5202
3137 1170 0345 6099 6352 6074 6142 1898 3657 1924 5625 3556 8178 0103 6107
3490 3349 7010 2045 6123 6271 8981 5274 2183 9820 0957 3988 6747 3508 8914
c) If Tevita decided to take a stratified sample based on amount owed by the debtors, according
to proportions in the population , then out of 500 accounts to be selected how many to be
selected from those owing less than $5000.
d) State first three accounts that will be selected for review from those account owning less than
$5000? Select the sample starting at the second digit of row 3 and working along the row.
e) Comment: is sample selection according to proportions in the population compulsory in
stratified sampling?
f) What other useful ways that can be used to stratify the account receivables account. What rule
to be applied while choosing a subgroup or stratum in stratified sampling?
g) A politician intends to collect sample data on voters age to estimate the population mean age
of voters in her electorate. Unfortunately, she does not have a complete list of voters. State
with a reason a sampling plan that would be suitable for her purposes.
h) Differentiate between sampling and non-sampling errors. Discuss ways to overcome these
errors.
i) Discuss the difference between an observational study and an experimental study.