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Qualitative data

Data that does not have numerical values or rankings, such as marital status and sex.

Quantitative data

Data that is reported as numerical quantities.

Nominal scale

A measurement scale that classifies data into distinct categories without a specific order.

Ordinal scale

A measurement scale that classifies data into categories with a meaningful order.

Interval scale

A measurement scale for continuous data that does not have a true zero point.

Ratio scale

A measurement scale that includes intervals with a true zero data point.

Bar chart

A graphical representation that shows the frequency of cases for categories of a discrete variable.

Line graph

A graphical representation used to display trends over time.

Pie chart

A graphical representation that shows the proportion of cases in several categories.

Mode

The number that occurs most frequently in a set of distribution.

Median

The middle point of a set of numbers when arranged in order.

Mean

The average of a set of numbers.

Bivariate associations

Relationships between two variables that may be related but are not necessarily causal.

Scatter plot

A graphical representation that shows the relationship between two quantitative variables.

Pearson correlation coefficient

A measure that expresses the extent of the linear relationship between two variables.

Contingency table

A table used to demonstrate the associations between two categorical variables.

Population

A collection of people who share common observable characteristics.

Sample

A subgroup that has been selected from the population.

Discrete variable

Data that can be counted and takes on distinct values, like household size.

Continuous variable

Data that can take any value within a range, such as heart rate or blood sugar levels.

Random sampling

A method of selecting a sample in which each member of the population has an equal chance of being chosen.

Nonrandom sampling

A method of selecting a sample that does not give all individuals in the population equal chances of being selected.

Convenience sampling

A nonrandom sampling method where the sample is taken from a group that is easily accessible.

Stratified sampling

A random sampling method that divides the population into subgroups and samples from each.

Systematic sampling

A nonrandom sampling method where members are selected at regular intervals from a sorted population.

Clustering sampling

A nonrandom sampling method that involves dividing the population into clusters and randomly selecting entire clusters.