Sampling

Question 1

What is a sample ?

Answer 1

The participants that you select from a target population to make generalisations about.

School children
Authority figures

Question 2

How do you know if the sample is representative of its target population ?

Answer 2

You can measure the extent to which the sample mirrors the target population.

Example - Can be generalised to larger population with accuracy.
Are the findings valid/reliable ?

Smaller samples are easier to collect data from so if they can be generalised it is more effective.

Question 3

volunteer sample ?

Answer 3

Where participants pick themselves through adverts/internet

Convenient - Ppts will want to engage in the study and easier as researcher doesn’t have to go and select people.

Unrepresentative - Bias - those who volunteer will likely have certain characteristics (confidence) so may not be generalisable to the wider population.

Question 4

Random sampling ?

Answer 4

Every member of population has equal chance of being selected.

Random selection - names in a hat - finding people in the street

For large samples it will be the most unbiased.

Time consuming - to make a list of all the possible people to choose from in the target population.

Question 5

Stratified sampling ?

Answer 5

Dividing the target population into subcategories.
Selecting members in the proportion that they occur in the population

Keeps the sample representative as it will hold an equal amount of people from each category.

Can be time consuming to calculate proportions and create the categories

Question 6

Stratified sampling how do you calculate it ?

Answer 6

Stratum size/Total population
Step 1 - Identify strata (the subcategories)

Step 2 - Determine sample size - how much is the overall sample size needed for the study.

step 3 - Calculate sample size per stratum - if a population has 60% women and 40% men the sample can have this amount.

Step 4 - Random selection - Within each stratum randomly select the specified number of individuals.

Question 7

Systematic sampling ?

Answer 7

Chooses sample in a logical way - every nth participant on a list of names.
Representative but can be difficult to achieve

Question 8

systematic sampling - how do you calculate it ?

Answer 8

Step 1 - Define population - Identify the group you want to study.

Step 2 - Sample size - How many individuals you need in your sample.

Step 3 - Calc sampling interval (find N) - Divide total population size by desired sample size.
1000 students/100 sample = 10 - Select every 10th person.

Step 4 - Random start point - select a n.o between 1 and the sampling interval.

Step 5 - Select the sample - From the random starting point select every nth individual from the list.

Question 9

Opportunity sampling ?

Answer 9

Using people from the target population that are available at the time/willing to join.
(Finding people in the street/study areas)

Quick/easy/cheap

Lacks representativeness so may be invalid