Visualizing Data with Charts and Graphs - Chapter 2

Vocabulary flashcards covering key terms related to frequency distributions and data visualization (both quantitative and qualitative) from Chapter 2.

Ungrouped data

Raw data that have not been summarized or organized into classes; observations listed individually.

Grouped data

Data that have been organized into logical groupings (class intervals) and assembled into a frequency distribution. (example: age ranges 20-29, 30-39, etc.)

Frequency distribution

A summary of data showing class intervals and the frequencies (counts) in each interval.

Class interval

A defined range of values used to group data in a frequency distribution (e.g., 1–under 3).

Class midpoint (class mark)

The value halfway across a class interval, calculated as the average of the interval’s endpoints.

Frequency

The number of observations that fall within a given class interval.

Relative frequency

The proportion of the total observations that fall in a given class (frequency divided by the total).

Cumulative frequency

The running total of frequencies through the classes in a distribution.

Range

The difference between the largest and smallest observations in a data set.

Histogram

A chart with contiguous rectangles representing frequencies for class intervals; x-axis shows intervals, y-axis shows frequencies; can be drawn with a distribution curve on top.

Distribution curve

A smooth curve over a histogram illustrating the theoretical distribution shape, often normal.

Frequency polygon

A graphical display of class frequencies using points at class midpoints connected by lines.

Ogive

A cumulative frequency polygon; x-axis uses class endpoints and y-axis shows cumulative frequencies.

Dot plot

A plot where each data value is represented by a dot; identical values stack vertically to show distribution and gaps.

Stem-and-leaf plot

A plot that splits digits into a stem (left) and a leaf (right); preserves original data while showing distribution.

Bar graph (bar chart)

A chart with bars representing categories; can be horizontal or vertical, used for qualitative or categorical data.

Pareto chart

A vertical bar chart that ranks categories from most to least frequent and often includes an ogive showing cumulative frequency.

Pie chart

A circular chart where the whole represents 100% and slices represent proportional shares; angles are proportional to the data and sum to 360 degrees.

Cross tabulation

A two-variable frequency table showing counts for combinations of two variables.

Scatter plot

A two-dimensional graph of paired numerical values used to assess possible relationships between variables.

Time series data

Data collected over time at regular intervals; visualized with a line chart to identify trends or directions.

Line chart

A chart that connects data points with a line, commonly used to display time series data.

Trend

The general direction in which data move over time in a time-series analysis.

Rotation to histogram

The process of converting grouped frequency data into a histogram by plotting class intervals against frequencies.

Number of classes (bins) rule of thumb

Choose between 5 and 15 classes (bins) when constructing a frequency distribution to balance detail and clarity.