data management

Sample

Small number of observations taken from the population; any data set that is not the whole population

Population

The entire group or total number of observations being studied

Statistics

The science of collecting, organizing, analyzing, and interpreting data

Why Study Statistics

It helps us evaluate information critically, avoid half-truths, and make practical decisions

Descriptive Statistics

Describes data using tables, graphs, and summary measures to make data manageable

Inferential Statistics

Makes generalizations or predictions about a population based on a sample

Measurement

Quantifying an observation using a rule, like thermometer for fever or exams for mental ability

Variable

Something that can be measured and can vary

Constant

Something that does not change and stays the same value

Scale of Measurement

The rule or level used to quantify an observation

Scales of Measurement

Nominal, Ordinal, Interval, Ratio

Nominal Scale

Categorical data where numbers are used as labels with no numerical meaning

Nominal Scale Example

Marital status labeled 1 = single, 2 = married (labels only)

Ordinal Scale

Ranked data showing greater-than or less-than, but not how much difference

Ordinal Scale Example

Fun run ranking without time differences

Interval Scale

Measurement data with meaningful intervals but no true zero

Interval Scale Example

Temperature in Celsius or Fahrenheit

Ratio Scale

Measurement data with meaningful intervals and a true zero

Ratio Scale Limitation

Cannot often be used in social sciences because absolute zero cannot be defined

Raw Data

Unorganized data collected directly from observations

Categorical Frequency Distribution

Organizes nominal or ordinal data into categories and frequencies

Examples of Categorical Data

Gender, business type, political affiliation

How to Construct a Frequency Distribution

Make a table, tally data, convert tallies to frequencies, compute percentages

Percentage Formula

Frequency ÷ total observations × 100

Grouped Frequency Distribution

Frequency distribution where data are arranged into class intervals

Class Interval

The width or numerical range for each class in grouped data

Determining Number of Classes

Depends on the method chosen by the researcher