Variables and data types
What kind of variable you have decides every choice after it: which graph, which summary, which test.
16 terms
Bivariate dataBivariate data records two variables on each observational unit, so you can study the relationship between them and not only each one alone.Categorical variableA categorical variable records which group or category an individual belongs to, rather than a numerical measurement.Continuous variableA continuous variable is a quantitative variable whose possible values fill an interval, so between any two of them there is always another.Count dataCount data are whole-number tallies of how many observational units fall in a category or how many times an event happened.Discrete variableA discrete variable is a quantitative variable whose possible values can be listed one by one, with nothing possible between two neighboring values.Explanatory variableAn explanatory variable is the one whose values are used to explain or predict the response variable; it goes on the x-axis of a scatterplot.MeasurementA measurement is the recorded value of a variable for one observational unit, reported on a scale and usually carrying units.Nominal variableA nominal variable is a categorical variable whose categories have no natural order, such as blood type, eye color, or brand of phone.Observational unitAn observational unit is the item or individual from which a datum is collected, that is, one row of the data set.Ordinal variableAn ordinal variable is a categorical variable whose categories have a meaningful order, but with no fixed numeric distance between them.ProportionA proportion is a part-to-whole fraction between 0 and 1, found by dividing the count in a category by the total number of observations.Quantitative variableA quantitative variable records a numerical measurement or count for which arithmetic such as averaging is meaningful.RateA rate divides a count by the size of the base it came from, such as time or population, so it carries units like per year or per 1,000.Response variableA response variable is the outcome an analysis is trying to account for; it supplies the y values and goes on the y-axis of a scatterplot.Univariate dataUnivariate data records one variable per observational unit, so the analysis describes a single distribution rather than a relationship.VariableA variable is a characteristic that can change from one observational unit to another, and it is what you record about each individual.