Statistics Chapter 1 Flashcards
What is the population?
The set of things we are interested in
What is the sample?
A subset of the population
What is a census?
Data collected from the whole population
What is the sampling frame?
A list of the population
What are the advantages of using a census?
Should give a completely accurate result as the whole population responds
What are the disadvantages of using a census? (3)
Time consuming and expensive
Can’t be used if texting destroys the item
Hard to process all of the data
What are the advantages of using a sample? (3)
Less time consuming and expensive
Fewer people have to respond
Less data to process
What are the disadvantages of using a sample? (2)
May not be as accurate
May not represent smaller sub-groups within the population
What is a simple random sample?
There is an equal chance for any unit to be picked as something like a random number generator is used
What are the advantages of doing using simple random sample? (3)
Free of bias
Easy and cheap for small populations
Known and equal chance of selection
What are the disadvantages of using a simple random sample? (2)
Not suitable for larger populations or sample sizes
A sampling frame is needed
What is a systematic sample?
The first unit is selected randomly and then the remaining units are selected at fixed intervals
What are the advantages of using a systematic sample? (2)
Simple and quick to use
Suitable for large samples and populations
What are the disadvantages of using a systematic sample? (2)
A sampling frame is needed
Bias can be introduced if the sampling frame is not random
What is stratified sampling?
Units are selected from the population in the correct proportion of each sub-group
What are the advantages of using stratified sampling? (2)
Sample accurately reflects the population
Guarantees proportional representation of sub-groups within the population
What are the disadvantages of using stratified sampling? (2)
Distinct strata are needed
Disadvantages from simple random sampling when selecting within strata
What is opportunity sampling?
The first units seen are tested; i.e. the first 12 people in a queue
What are the advantages of using opportunity sampling? (2)
Easy to carry out
Inexpensive
What are the disadvantages of using opportunity sampling? (2)
Unlikely to provide a representative sample
Highly dependent on individual researcher
What is a quota sample?
The sample reflects the characteristics of the population; certain criteria are set and a certain number of units fitting the criteria are tested
What are the advantages of using a quota sample? (4)
Small sample can still be representative
No sampling frame needed
Quick, easy and inexpensive
Easy comparison of groups within a population
What are the disadvantages of using a quota sample? (4)
Non-random sampling can introduce bias
Dividing the population may be inaccurate
Increasing the scope of the study increases the number of groups needed
Non-responses are not recorded
How is stratified sampling calculated?
number in stratum / total frequency x sample size
