Sampling Flashcards
What does it mean if data is qualitative?
When data can be in categories eg flavour of cupcakes of place of birth
What does it mean if data is discrete?
The data can only take individual distinct values eg number of siblings or shoe size
What does it mean if data is continuous?
Something that can be measured and recorded to any accuracy eg height or weight
What is a population in sampling?
All the possible values a variable can take eg heights of all adult females
When are samples used?
If It is impossible or not advisable to investigate the whole population, usually as it would be impractical or destructive
Eg
You can’t interview everyone in the uk
And to test the lifespan of an entire population of lightbulbs would destroy all the lightbulbs
Why does the sample need to be as representative of the population as possible?
The sample will be used to draw conclusions about the population
What is a parameter?
A statistical measure of the entire population eg standard deviation or mean height of all women in uk
What is a statistic?
A statistical measure carried out on a sample eg mean height of a sample of women in the uk
Population => Parameter
Sample => Statistic
Define a truly random sample
A random sample of size n is a sample selected in such a way that all possible samples of size n have an equal chance of being selected
What is a simple random sample?
A random sample that does not allow any repetition (without replacement)
In simple random sampling how are numbers picked?
Random number generator
Give some advantages and disadvantages of simple random sampling
Advantages
Most statistical methods assume a random sample
Only method which is truly random
Disadvantages
Can be very time consuming
With large target population can be impossible to carry out
List of whole population needed
What is opportunity sampling?
Taking the sample from people who are available at the time the study is being carried out and fit the criteria you are looking for
Eg you use the first 20 people who enter the dining room
What are some advantages and disadvantages of opportunity sampling?
Advantages
May save time and money
Can be seen as adequate when investigating processes which are thought to work in similar ways for most individuals such as memory processes.
Disadvantages
Likely to produce a sample not representative of the population
Researcher may choose people from their own social and cultural group
Some people may refuse to take part making the sample self selecting