Sampling and Statistics (Exam #2 social research methods) Flashcards
systematic sampling error
An error that arises from some basic defect in the sampling or preparation process such that the result obtained is always either higher or lower than the true figure
Random sampling
A method of sampling that relies on a random, or chance, selection method so that every element of the sampling frame has a known probability of being selected
Random assignment
A procedure by which each experimental subject is placed in a group randomly
Probability sampling
Sampling methods that rely on a random, or chance, selection method so that the probability of selection of population elements is known
non-probability sampling
Sampling methods in which the probability of selection of population elements is unknown
target population
A set of elements larger than or different from the population sampled and to which the researcher would like to generalize study findings
sampling frame
A list of all elements or other units containing the elements in a population
simple random sampling
A method of sampling in which every sample element is selected purely on the basis of chance through a random process
systematic random sampling
A method of sampling in which sample elements are selected from a list or from sequential files, with every nth element being selected after the first element is selected randomly
what are the four most common types of probability (random) sampling
simple random sampling, systematic random sampling, cluster sampling, and stratified random sampling
stratified random sampling (proportionate vs. disproportionate)
A method of sampling in which sample elements are selected separately from population strata that the researcher identifies in advance
ex) strata is race, income, gender, SES… age
Cluster sampling
Sampling in which elements are selected in two or more stages, with the first stage being the random selection of naturally
occurring clusters and the last stage being the random selection of elements within clusters
Random assignment is associated with what type of validity?
internal validity
Random sampling is associated with what type of validity?
external validity
proportionate stratified random sampling
Sampling method in which elements are selected from strata in exact proportion to their representation in the population
pro: eliminates any possibility of sampling error
disproportionate stratified random sampling
Sampling in which elements are selected from strata in proportions different from those that appear in the population (the probability of selection
of every case is known but unequal between strata)
single-stage cluster sampling
multistage cluster sampling
clusters within clusters
primary sampling units
Units listed at each stage of a multistage sampling design
availability / convenience sampling
Sampling in which elements are selected on the basis of convenience
ex. Popular magazines periodically survey their readers by printing a questionnaire for readers to fill out and mail in.
Quota sampling
A nonprobability sampling method in which elements are selected to ensure that the sample represents certain characteristics in proportion to their prevalence in the population
hint: looking at trends
ex. brand perference amongst age groups
purposive / judgmental sampling
A nonprobability sampling method in which elements are selected for a purpose, usually because of their unique position
three guidelines for selecting informants when designing any purposive sampling strategy. Informants should be:
- Knowledgeable about the cultural arena, situation, or experience being studied;
- Willing to talk
- Representative of the range of points of view
random sampling error
descriptive statistics
Statistics used to describe the distribution of and relationship among variables
inferential statistics
Statistics used to estimate how likely it is that a statistical result based on data from a random sample is representative of the
population from which the sample is assumed to have been selected
Mode
The most frequent value in a distribution
Mean
The arithmetic, or weighted, average computed by adding the value of all the cases and dividing by the total number of cases
Median
The position average, or the point, that divides a distribution in half (the 50th percentile)
Variance
A statistic that measures the variability of a distribution as the average squared deviation of each case from the mean
standard deviation
The square root of the average squared deviation of each case from the mean
Matrix
A chart used to condense qualitative data into simple categories and provide a multidimensional summary that will facilitate subsequent, more intensive analysis
internal consistency / inter-item reliability
An approach that calculates reliability based on the correlation between multiple items used to measure a single concept
if items are highly correlated
Example of descriptive statistics?
mean, median, mode, standard deviation, range, variance
What happens when the sample size increases?
the range will increase/ be larger (more data, more variation) + catch an OUTLIER!!- increases the rang
What does Inferential Statistics do?
- Estimate pop characteristics from sample
- Test hypotheses about relationships
