1.2 Sampling

Question 1

What happens in random sampling?

Answer 1

» Every member of the population has an equal chance of being selected

Question 2

What is bias?

Answer 2

» Bias is a disproportionate weight in favor of or against an idea or thing

Question 3

What are the methods of random sampling?

Answer 3

» Simple random
» Systematic sampling
» Stratified samping

Question 4

What are the steps to carry out a simple random sample?

Answer 4

» You need a sampling frame
» Allocate the objects to a unique number and a selection of these numbers is chosen at random

Question 5

What are the 2 methods of choosing the numbers?

Answer 5

» Generating random numbers
» Using lottery sampling

Question 6

What is lottery sampling

Answer 6

» The members of the sampling frame could be written on tickets and place into the hat
» The required number of tickets would then be drawn out

Question 7

What is systematic sampling?

Answer 7

» In systematic sampling, the required elements are chose at regular intervals from an ordered list

Question 8

What is one key thing you need to do for the first person to be chosen in systematic sampling?

Answer 8

» Has to be chosen at random, perhaps using a random number generator

Question 9

What is stratified sampling?

Answer 9

» The population is divided into mutually exclusive strata, such as males and females
» Random sample is taken from each

Question 10

What should the proportion of each sampled be?

Answer 10

» The same
» Do this by doing the number of people in the stratum / number in population times the overall sample size

Question 11

What are the advantages of simple random sampling?

Answer 11

» Free of bias
» Easy and cheap to implenent
» Each sampling unit has a equal chance of selection

Question 12

What are the disadvantages of simple random sampling?

Answer 12

» Not suitable when population size is very large, as it can be time consuming
» A sampling frame is needed

Question 13

What are the advantages of systematic sampling?

Answer 13

» Simple and quick to use
» Suitable for large samples and large populations

Question 14

What are the disadvantages of systematic sampling?

Answer 14

» A sampling frame is needed
» It can introduce bias if the sampling frame is not random

Question 15

What are the advantages of stratified sampling?

Answer 15

» Reflects accurately the population structure
» Guarantees proportional representation of groups within a population

Question 16

What are the disadvantages of stratified sampling?

Answer 16

» Population must be clearly classified into distinct strata
» Sampling frame is needed
» Not suitable when population size is very large