Data Collection Flashcards
1
Q
What is a population?
A
- A collection of the whole of something
- All elements sharing some set of characteristics;
- If we have a population we can get parameters - true values
- Census
- A study of all elements of a population
2
Q
What is a sample?
A
- A set of individuals drawn from a population
- If we have a sample we can get statistics - values that estimate the parameter
- Sample characteristics = statistics
- Needs to be representative of full population
3
Q
What kinds of error are there?
A
- Sampling error
* Non-sampling errors
4
Q
What is sampling error?
A
- The difference that exists between a population and a sample as a result of the sample selection.
- Will be reduced by taking a larger sample
5
Q
Why are non-sampling errors a problem and what kinds are there?
A
- Larger samples won’t reduce non sampling errors so more serious
- Coverage error
- Nonresponse error
- Measurement Error
6
Q
What is coverage error and how is it reduced?
A
- Results from selection bias
- No matter what, some people will never be in sample
- Reduced by having an adequate sampling frame (up to date list of all items from which you will select the sample)
7
Q
What is non-response error?
A
- Some people will never choose to do surveys
- Upper and lower economic classes have differing survey response frequency
- Can’t assume that people who do respond to surveys are the same as those who don’t
8
Q
What is measurement error?
A
- Ambiguous wording of questions
- Hawthorne effect
- Respondent feels obliged to please the interviewer
- Respondent error
9
Q
What are the steps to taking a sample?
A
- Define the sample frame
- Choose nonprobabliity or probability sampling
- Chose a sampling plan
10
Q
What is a sample frame?
A
- A list of all the items that make up the population
- Choice of frame important
- Sample is then chosen from the sample frame
11
Q
What is the difference between probability and non-probabilty sampling?
A
- Non probability sampling
- Choose the items to be included without knowing their
probabilities of selection - Cannot apply stasitical inferences
- Cheap and dirty
- Choose the items to be included without knowing their
- Probability sampling
- Select items based on known probabilities
- Statistical inferences allowed
12
Q
What are the non-probability sampling plans?
A
- Convenience
- Judgemental
- Quota
- Snowball
13
Q
What are the probability sampling plans?
A
- Simple random
- Systematic
- Stratified
- Cluster
14
Q
What is cluster sampling?
A
- Divides the population into clusters, a number of clusters is selected to represent the population and all units within selected clusters are included in the sample
- Cheap, easy, reduced field work
- Imprecise, difficult to compute and interpret results
- Properties, households, homes
15
Q
What is stratified sampling?
A
- The population is divided into groups called strata from which a simple random sample is drawn
- Objective is to form strata such that the population values of interest within each stratum are as much alike as possible
- Includes all important sub-populations, precision
- Difficult to select relevant stratification variables, not feasible to stratify on many variables
