Statistics Chapter 1 - Data Collection

Question 1

Population

Answer 1

the whole set of items that are of interest

Question 2

Sample

Answer 2

a selection (subset) of data from the population

Question 3

Census

Answer 3

collection of all data from a whole population

Question 4

Sampling unit

Answer 4

individual units of a population

Question 5

Sampling frame

Answer 5

a list of individually named or numbered sampling units

Question 6

Simple random sampling

Answer 6

• use a random number generator or a lottery
• every sampling unit has an equal chance of being selected

Question 7

Advantages of simple random sampling

Answer 7

• free of bias
• easy and cheap
• no prior knowledge of the population needed
• every unit has equal chance of being selected

Question 8

Disadvantages of simple random sampling

Answer 8

• can be unrepresentative
• time-consuming
• sampling frame is required

Question 9

Systematic sampling

Answer 9

• the required elements are chosen at set intervals
• the first element chosen is random

Question 10

Advantages of systematic sampling

Answer 10

• simple and quick
• suitable for large populations

Question 11

Disadvantages of systematic sampling

Answer 11

• sampling frame is required
• can introduce bias if sampling frame is not random

Question 12

Stratified sampling

Answer 12

• separate population into mutually exclusive strata (categories)
• take a random sample from each, in the same proportion as the population (e.g. if there are 8 boys and 12 girls in a class, each strata must have a 2:3 ratio of boys to girls)

Question 13

Advantage of stratified sampling

Answer 13

• each strata is represented in the sample
• more representative of the population

Question 14

Disadvantages of stratified sampling

Answer 14

• need to separate into distinct strata
• same as simple random sampling within strata

Question 15

Quota sampling

Answer 15

• similar to stratified but not random
• split into categories and collect data until each category has fulfilled quota (e.g., pick the first five most convenient people after walking into Sixth Form Zone)

Question 16

Advantages of quota sampling

Answer 16

• still can be representative of population
• does not require sampling frame

Question 17

Disadvantages of quota sampling

Answer 17

• can introduce bias
• requires population to be split into categories
• non-respondents are not recorded

Question 18

Opportunity/convenience sampling

Answer 18

find the first n samples and stop

Question 19

Advantage of opportunity/convenience sampling

Answer 19

easy and convenient

Question 20

Disadvantages of opportunity/convenience sampling

Answer 20

• can be biased
• can be unrepresentative

Question 21

Quantitative data

Answer 21

numerical data

Question 22

Qualitative data

Answer 22

non-numerical data

Question 23

Continuous data

Answer 23

can take any value (e.g., height, weight, density)

Question 24

Discrete data

Answer 24

can only take certain values (e.g., shoe size, number of pets)