Chapters 14, 15 & 16 Flashcards
What is a sample?
A sample is a special subset of a population that is observed for purposes of making inferences about the nature of the population itself
What is purposive sampling (a.k.a judgmental sampling)?
A type of non-probability sampling method in which the researcher uses his or her own judgment in selecting sample members.
When informants are used, how should they be selected?
In such a fashion as to provide a broad, diverse view of the group under study.
True or false: In general, non-probability sampling methods are regarded as less reliable than probability sampling methods.
True
True or false: non-probability sampling methods are harder and more expensive to use than probability sampling methods
False (they are often easier and cheaper to use)
What is the chief criterion of the quality of a sample?
The degree to which it is representative (the extent to which the characteristics of the sample are the same as those of the population from which it was selected).
True or false: probability sampling methods provide one excellent way to select samples that will be quite representative.
True
What is the chief principle of probability sampling?
Every member of the total population must have the same known, nonzero probability of being selected into the sample.
Can the most carefully selected sample perfectly represent the population from which it was selected?
No, it will almost never be perfectly representative. There will always be some degree of sampling error.
Probability sampling methods allow us to ___ the amount of sampling error that should be expected in a given sample.
estimate
What is a sampling frame?
A sampling frame is a list or quasi-list of the members of a population. It is the resource used in the selection of a sample. A sample’s representativeness depends directly on the extent to which a sampling frame contains all the members of the total population that the sample is intended to represent.
Simple random sampling is ___ the most fundamental technique in probability sampling.
logically
Systematic sampling involves the selection of every ___ member from a sampling frame. This method is functionally equivalent to simple random sampling, with a few exceptions.
kth
___ is the process of grouping the members of a population into relatively homogenous strata before sampling. This practice improves the representativeness of a sample by reducing the degree of sampling error.
Stratification
What is the complex sampling technique that is used in those cases in which a list of all the members of a population does not exist?
multistage cluster sampling
Describe multistage cluster sampling: (3)
- An initial sample of groups of members (clusters) is selected
- All members of the selected cluster are listed, often through direct observation in the field
- The members listed in each selected cluster are subsampled, thereby providing the final sample of members
What is PPS? (hint: it is a special, efficient method for multistage cluster sampling)
Probability proportionate to size
If the members of a population have unequal probabilities of selection into the sample, it is necessary to assign ___ to the different observations made in order to provide a representative picture of the total population.
weights (basically, the weight assigned to a particular sample member should be the inverse of its probability of selection)
In the 1948 Gallup poll that predicted that Thomas Dewey would defeat Harry Truman, in what major way could Gallup have modified his design to avoid the error?
Increased the representativeness of his quota sample (his data was from a pre-WWII census that did not represent rural to urban migration, and that city dwellers were more likely to vote democratic)
___ ___ should be avoided in sampling.
Gender bias
What is survey research?
The administration of questionnaires to a sample of respondents selected from some population.
What is survey research especially appropriate for?
For making descriptive studies of large populations, as well as for explanatory purposes.
In 3 ways can questionnaires be administered?
- Self-administered questionnaires can be completed by the respondents themselves
- Interviewers can administer questionnaires in face-to-face encounters, reading the items to respondents and recording the answers
- Interviewers can conduct telephone surveys