sampling

Question 1

What are the types of sampling?

Answer 1

• opportunity
• random
• volunteer
• systematic
• stratified

Question 2

What is opportunity sampling?

Answer 2

Recruit those people who are most convenient or most available

Question 3

What are the strengths for opportunity sampling?

Answer 3

• Easiest method because you use the first suitable person you find
• Less time to locate sample

Question 4

What are the limitations for opportunity sampling?

Answer 4

Bias - sample is drawn from a small part of the population

Question 5

What are the two types of random sampling?

Answer 5

• lottery method
• random number generator

Question 6

What is the lottery method? and how does it work?

Answer 6

• Draw numbers or names from a hat
• Obtain a list of all people in the population
• Put all names in a hat/lottery barrel
• Select the number of names required

Question 7

What is the random number generator? and how does it work?

Answer 7

• Calculators have functions that generate random numbers as do computers and apps on phones
• Number every member of the population
• Using for example excel, generate a random number from 1-100 for example

Question 8

What are strengths for random sampling?

Answer 8

Unbiased - all members of the target population have an equal chance of being selected

Question 9

What are the limitations for random sampling?

Answer 9

Time consuming - needs a list of all members of population and have to contact them all separately

Question 10

What is volunteer sampling?

Answer 10

advertised in a newspaper or on a notice board on the internet

Question 11

What are strengths for volunteer sampling?

Answer 11

Gives access to a variety of ppts - may make the sample more representative and a less bias sample

Question 12

What are limitations for volunteer sampling?

Answer 12

Biased in other ways - ppts are likely to be more highly motivated (to be helpful/need money) with more time on their hands - results in volunteer bias

Question 13

What is systematic sampling?

Answer 13

• Use a predetermined system to select ppts (such as every 6th, 14th, 20th person from a phonebook)
• The numerical interval is applied consistently

Question 14

What are strengths for systematic sampling?

Answer 14

Unbiased as participants are selected using an objective system

Question 15

What are limitations for systematic sampling?

Answer 15

Not truly unbiased/random unless you select a number using a random method and start with this person, and then select every nth person

Question 16

What is stratified sampling?

Answer 16

• Subgroups (or strata) within a population are defined e.g. 10-12 year olds
• Ppts are obtained from each of the strata in proportion to their occurrence in the population.
• Selection is carried out using random sampling

Question 17

What are strengths for stratified sampling?

Answer 17

• Unbiased - ppts are selected using an objective system
• Likely to be more representative than other methods - there is a proportional and randomly selected representation of subgroups

Question 18

What are limitations for stratified sampling?

Answer 18

• Not truly unbiased/random unless you select a number using a random method and start with this person, and then select every nth person
• Very time consuming to identify the subgroups , then randomly select ppts and contact them