Sample
A subset of a population used to study the population as a whole
Elements
The individual members of the population whose characteristics are to be measured
Sampling frame
A list of all elements or other units containing the elements in a population
Census
Research in which information is obtained through responses from or information about all available members of an entire poplation
sample generalizability
A conclusion based on a sample, or subset, of a larger population holds true for that population
cross-population generalizability
When findings about one group, population, or setting hold true for other groups, populations, or settings
Probability Sampling
Sampling method that relies on a random, or chance, selection method so that the probability of selection of population elements is known
Nonprobability Sampling
Sampling methods in which the probability of selection of population elements is not known
Simple Random Sampling
Identifies cases strictly on the basis of chance
Systematic Sampling
A sample in which every nth unit in a list is selected for inclusion in the sample
Stratified Random Sampling
A method of sampling in which sample elements are selected separately from population strata that the researcher identifies in advance
Proportionate Stratified Sampling
Elements are selected from the strata in exact proportion to their representation in the population
Disproportionate Stratified Sampling
Elements are selected from strata in proportions different from those that appear in the population
Multistage 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
Convenience/Availability Sampling
Sampling in which elements are selected on the basis of convenience
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
Purposive Sampling
A nonprobaility sampling method in which elements are selected for a purpose, usually because of their unique position
Snowball Sampling
A method of sampling in which sample elements are selected as successive informants or interviewees identify them
Omnibus Survey
A survey that covers a range of topics of interest to different social scientists
Questionnaire
A survey instrument containing the questions in a self-administered survey
Interview Schedule
A survey instrument containing the questions asked by the interviewer in an in-person or phone survey
Double-Negative Question
A question or statement that contains two negatives, which can muddy the meaning of the question
Double-Barreled Question
A single survey question that actually asks two questions but allows only one answer
Pre-test
Administering a questionnaire to a limited number of potential respondents and other individuals capable of pointing out design flaws
Context Effects
In survey research, refers to the influence that earlier questions may have on how subsequent questions are answered
Fence-Sitters
Survey respondents who see themselves as being neutral on an issue and choose a middle (neutral) response that is offered
Floaters
Survey respondents who provide an opinion on a topic in response to a closed-ended questions that does not include a "don't know" option but will choose "don't know" if available
Filter Question
A survey question used to identify a subset of respondents who then are asked other questions
Statistic
A numeric description of some feature of a variable or variables in a sample from a larger population
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
Frequency Distribution
Numerical display that shows the number of cases, and usually the percentage of cases (the relative frequency), corresponding to each value or group of values of a variable
Skewness
Extent to which cases are clustered more at one or the other end of the distribution of a quantitative variable rather than in a symmetric pattern around its center
Central Tendency
The most common value (for variables measured at the nominal level) or the value around which cases tend to center (for a quantitative variable)
Bar Chart
A graphic for qualitative variables in which their variable's distribution is displayed with solid bars separated by spaces
Histogram
A graphic for quantitative variables in which the variable's distribution is displayed with adjacent bars
Frequency Polygon
A graphic for quantitative variables in which a continuous line connects data points representing the variable's distribution
Time Series Chart
A graphic displayed change in two or more variables at different points in time
Pie Chart
A graphic in which categories are displayed as segments of a circle whose pieces add up to 100%
Mode
The most frequent value in a distribution
Median
The position average, or the point, that divides a distribution in half (the 50th percentile)
Mean
The arithmetic, or weighted, average computed by adding the value of all the cases and dividing by the total number of cases
Range
The true upper limit in a distribution minus the true lower limit
Interquartile range
The range in a distribution between the end of the 1st quartile and the beginning of the 3rd quartile
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
Normal Distribution
A symmetric distribution shaped like a bell and centered around the population mean, with the number of cases tapering off in a predictable pattern on both sides of the mean
Cross-tabulation
A bivariate distribution showing the distribution of one variable for each category of another variable; can also be elaborated using three or more variables
Statistical Significance
The mathematical likelihood that an association is not the result of chance, judged by a criterion the analyst sets
Elaboration analysis
The process of introducing a third variable into an analysis to better understand the bivariate relationship under consideration; additional control variables also can be introduced
Secondary Data Analysis
The method of using preexisting data in a different way or to answer a different research question than intended by those who collected the data
Survey Research
Research in which information is collected from a sample of individuals through their responses to a set of standardized questions