Statistics definitions

Question 1

What is a population?

Answer 1

The whole set of items that are of interest.

Question 2

What does a census do?

Answer 2

It measures every member of a population.

Question 3

What is a sample?

Answer 3

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

Question 4

What are sampling units?

Answer 4

Individual units of a population.

Question 5

What is a sampling frame?

Answer 5

A list of individually named or numbered sampling units of a population.

Question 6

What are the three methods of random sampling?

Answer 6

• Simple random sampling
• Systematic sampling
• Stratified sampling

Question 7

What is a simple random sample?

Answer 7

One where every sample has an equal chance of being selected.

Question 8

What is a systematic sample?

Answer 8

One where the required elements are chosen at regular intervals from an ordered list.

Question 9

What is a stratified sample?

Answer 9

One where the population is ordered into mutually exclusive strata and a random sample is taken from each.

Question 10

What are the advantages of simple random sampling?

Answer 10

• Free of bias
• Easy and cheap for small populations and samples
• Each sampling unit has a known and equal chance of selection

Question 11

What are the disadvantages of simple random sampling?

Answer 11

• Not suitable when the population or sampling size is large

- A sampling frame is needed

Question 12

What are the advantages of systematic sampling?

Answer 12

• Simple and quick

- Suitable for large samples and populations

Question 13

What are the disadvantages of systematic sampling?

Answer 13

• A sampling frame is needed

- It can introduce bias if the sampling frame is not random

Question 14

What are the advantages of stratified sampling?

Answer 14

• Sample accurately reflects the population structure

- Guarantees proportional representation of groups within a population

Question 15

What are the disadvantages of stratified sampling?

Answer 15

• Population must be clearly classified into distinct strata

- Selection within each stratum suffers from the same disadvantages as simple random sampling

Question 16

What are the two types of non-random sampling?

Answer 16

Quota sampling and opportunity sampling.

Question 17

What is a quota sample?

Answer 17

One where an interviewer or researcher selects a random sample that reflects the characteristics of the whole population.

Question 18

What is an opportunity sample?

Answer 18

One where a sample is taken from people who are available at the time the study is carried out and people who fit the criteria you are looking for.

Question 19

What are the advantages of quota sampling?

Answer 19

• Allows a small sample to still be representative of the population
• No sampling frame needed
• Quick easy and inexpensive
• Allows for easy comparison between different groups within a population

Question 20

What are the disadvantages of quota sampling?

Answer 20

• Can introduce bias
• Population must be divided into groups which can be costly or inaccurate
• Non-responses are recorded as such

Question 21

What are the advantages of opportunity sampling?

Answer 21

• Easy to carry out

- Inexpensive

Question 22

What are the disadvantages of opportunity sampling?

Answer 22

• Unlikely to provide a representative sample

- Highly dependent on individual researcher

Question 23

What is a continuous variable?

Answer 23

One that can take any value in a given range.

Question 24

What is a discrete variable?

Answer 24

One that can only take specific values in a given range.