statistics

the science of collecting, analyzing and drawing conclusions from data.

population of interest

the entire collection of individuals or objects about which information is desired.

sample

a subset of the population, selected for study in some prescribed manner.

descriptive statistics

methods for organizing and summarizing data.

inferential statsitics

generalizing from a sample to the population from which it was selected.

univariate data set

a data set consisting of observations on a single attribute.

categorical data (qualitative)

if the individual observations are categorical responses.

numerical data (quantitative)

if each observation is a number.

bivariate data set

a data set consisting of observations on two different attributes.

multivariate data set

a data set consisting of observations for each of two or more attributes.

numerical data: discrete

if the possible values are isolated points on the number line.

numerical data: continuous

if the set of possible values forms an entire interval on the number line.

frequency distribution for categorical data

a table that displays the possible categories along with the associated frequencies or relative frequencies.

frequency

for a particular category, it is the number of times the category appears in the data set.

relative freqency

for a particular category, it is the fraction or proportion of the time that the category appears in the data set, it is calculated as: relative frequency = frequency/number of observations in the data set

relative frequency distribution

when the table includes relative frequencies.

bar chart

a graph of the frequency distribution of categorical data.

dotplot

a simple way to display numerical data when the data set is reasonably small.