Data Types and Visualization

Overview

This lecture introduces key concepts about data types and how to organize and display quantitative data using tables, bar graphs, and line graphs.

Quantitative data deals with numerical information.
Continuous data can take any value within a range and has infinite possible values between any two points (e.g., measured weights).
Discrete data has specific, separate values with no in-between values (e.g., number of ice cream flavors).
Continuous data is typically measured, while discrete data is usually counted.

Data should be organized to avoid confusion and make interpretation easier.
Data tables organize information in rows and columns, with each intersection called a cell.
Columns and rows have labels to clarify what the data represents.
Tables can be formatted horizontally or vertically without changing the data.

Graphs visually represent data using elements like bars, lines, or points.
Bar graphs use rectangular bars to represent numeric values, making comparisons easier.
Axes on a graph are labeled; the vertical axis (y-axis) usually shows values, and the horizontal axis (x-axis) shows categories or time.
The height of a bar matches the value from the data table.

The range of values shown on the axis is called the scale (includes minimum, maximum, and interval).
Choosing the right scale and interval is crucial for clear data representation.
Bar graphs can also display negative values by extending the axis below zero.

Line graphs connect data points with lines to show changes over time or trends.
Line graphs are ideal for showing patterns, trends, or changes in data sets, especially over time.
Grids help accurately locate and compare data points in a line graph.
Multiple data sets can be shown on one line graph using different colors or line styles.

Bar graphs are best for categorical data or discrete data with unrelated categories.
Line graphs are best when data points are sequential (such as time) and trends between points matter.
Using a line graph with unrelated categories can be misleading.

Quantitative Data — numerical data representing amounts or quantities.
Continuous Data — data with any value within a range (measured).
Discrete Data — data with specific, separate values (counted).
Data Table — organized display of data in rows and columns.
Cell — the intersection box of a data table’s row and column.
Graph — visual representation of data.
Bar Graph (Bar Chart) — graph that uses bars to show data values.
Axis (Axes) — labeled sides of a graph (x-axis and y-axis).
Scale — range of values represented on a graph’s axis.
Interval — size of each step between numbers on a graph’s axis.
Line Graph — graph that connects data points with line segments to show trends.
Trend — pattern or general direction in data over time.

Practice reading and interpreting bar graphs and line graphs.
Try answering practice problems using data tables and different types of graphs.