Data Collection

Question 1

Define population:

Answer 1

A whole set of items that are in interest

Question 2

Define census:

Answer 2

Something that observes or measures every member of a population.

Question 3

Define a sample:

Answer 3

A selection of observations taken from a subset of the population, which is used to find out information about the whole of the population.

Question 4

What is the advantage of a census compared to a sample?

Answer 4

Should give a completely accurate result.

Question 5

What are the 3 disadvantages of a census compared to a sample?

Answer 5

Time consuming and expensive.
Can’t be used when the testing process destroys the item.
Hard to process large quantity of data.

Question 6

What are the 3 advantages of a sample compared to a census?

Answer 6

Less time consuming and expensive.
Fewer people have to respond.
Less data to process.

Question 7

What are the 2 disadvantages of a sample compared to a census?

Answer 7

May not be as accurate.

Sample may not be large enough to give information about small sub-groups of the population.

Question 8

Define sampling units:

Answer 8

Individual units of a population.

Often individually named or numbered to form a list called a sampling frame.

Question 9

Name the 3 types of random sampling:

Answer 9

Simple random sampling.
Systematic sampling.
Stratified sampling.

Question 10

Define random sampling:

Answer 10

When every member has an equal chance of being selected so the sample should be representative to the population.
Removes bias.

Question 11

Give 2 types of non-random sampling:

Answer 11

Quota sampling.

Opportunity sampling.

Question 12

Define simple random sampling:

Answer 12

. If there is a simple random sample of size n, every member of sample size n has an equal chance of getting selected.
. Often used for lotteries and members are chosen through hat or calculator.

Question 13

Define systematic sampling (with example):

Answer 13

When required elements are chosen at regular intervals from an ordered list.
E.g. if sample size 20 is required from population 100, take every 5th person since 100➗20=5. First member to be chosen should be at random but between 1 and 5 so if first member is 2, then member 2,7,12,17 get chosen and so on.

Question 14

Define stratified sampling:

Answer 14

When population is divided into mutually exclusive data (for example males and females) and proportion of each strata sampled should be same.
- This is done with the formula: Number in stratum➗number in population X overall sample size.

Question 15

Define quota sampling:

Answer 15

. Proportion of people selected in should be the same in each quota but unlike stratified sampling (use same formula), you have to find people who match the characteristics of that quota until you have filled up the number required for each quota, instead of knowing previously who has the characteristics required.

Question 16

Define opportunity sampling (with example):

Answer 16

. Involves taking a sample from people who are available at the time the study is carried out and who fits the criteria you are looking for.
. For example it could be the first 20 people outside a supermarket who are carrying bags.

Question 17

Give 2 opportunity sampling advantages:

Answer 17

. Easy to carry out.

. Inexpensive.

Question 18

Give 2 opportunity sampling disadvantages:

Answer 18

. Unlikely to provide a representative sample.

. Highly dependent on individual researcher.

Question 19

Give 3 quota sampling disadvantages:

Answer 19

. Bias.
. Dividing population into groups can be costly and inaccurate.
. Non-responses aren’t recorded.

Question 20

Give 3 quota sampling advantages:

Answer 20

. No sampling frame required.
. Quick, easy and inexpensive.
. Allows for easy comparison between different groups within a population.