STATS Flashcards
What is Simple Random Sampling?
Where every sample in a population had an equal chance of being select.
What are the two types of simple random sampling?
assigning each member of a population a number and then generating random numbers, lottery (each person has a ticket and pick out of a hat)
Advantages of Simple Random Sampling
Removes bias, easy and cheap for small samples, equal chance of selection
What is systematic sampling?
The required elements are chosen at regular intervals from an ordered list
How to take a systematic sample?
n- population
s- sample size
the interval is n/s, the first person to be chosen should be at random
What is stratified sampling?
When the population is divided into mutually exclusive strata (eg males and females) and a random sample is taken from each
Disadvantages of Simple Random Sampling
Not suitable for large population, sampling frame is needed
Advantages of Systematic Sampling
Simple and Quick to use, Suitable for large populations
Disadvantages of Systemstic Sampling
A sampling frame is needed, can introduce bias if the sampling frame is not random.
Advantages of Stratified Sampling
Sample accurately reflects the population structure, guaranteed proportional representation
Disadvantages of Stratified Sampling
Population must be clearly classified into distinct strata, have to simple random sample each strata
What are the two methods of Non random sampling?
Quota Sampling, Opportunity sampling
What is Quota Sampling?
an interviewer or researcher selects a sample that reflects the whole population
How do you implement Quota Sampling?
The population is divided into groups according to a characteristic, the size of each group determines the proportion of the sample that has it. An interviewer meets people, assesses they’re group and allocate them to the appropriate quota.
What is Opportunity Sampling?
Takes the sample from people who are available at the time the study is carried out and who fit the criteria.
Advantages of Quota Sampling
Allows a small sample to still be representative, No sampling frame required, Quick easy and inexpensive, Allows for easy comparison between different groups.
Disadvantages of Quota Sampling
Can introduce bias, population must be divided into groups which can be costly or inaccurate, Not suitable for large groups
Advantages of Opportunity Sampling
Easy to carry out, inexpensive
Disadvantages of Opportunity Sampling
Unlikely to be representative, dependant on researcher
What is a quantative variable?
a variable you can assign a numerical value to (eg shoe size)
What is a qualitative variable?
A variable you cannot assign a numerical value to
What is a continuous variable?
A variable that can take any value in a given range (eg time)
What is a discrete variable?
A variable that can take only specific values in a range
