Unit 3 : Frequency Distributions and Their Graphs

Vocabulary flashcards covering core definitions and concepts related to frequency distributions, class boundaries, measures of frequency, and visual graphs.

Frequency Distribution

A table or method that organizes and summarizes data by showing classes or intervals of data entries along with the count of entries (frequency $f$) in each class.

Class Frequency ($f$)

The number of data entries in a specific class of a frequency distribution.

Lower Class Limit

The least number that can belong to a class in a frequency distribution.

Upper Class Limit

The greatest number that can belong to a class in a frequency distribution.

Class Width

The distance between lower (or upper) limits of consecutive classes in a frequency distribution.

Midpoint (Class Mark)

The sum of the lower and upper limits of a class divided by two, calculated as $\text{Midpoint} = \frac{(\text{Lower class limit}) + (\text{Upper class limit})}{2}$.

Relative Frequency

The portion, or percentage, of the data that falls in a class, calculated as $\text{Relative frequency} = \frac{f}{n}$, where $f$ is class frequency and $n$ is sample size (n = \text{\textSigma} f).

Cumulative Frequency

The sum of the frequencies of a given class and all previous classes, where the cumulative frequency of the last class equals the sample size $n$.

Class Boundaries

The numbers that separate classes without leaving gaps between them, calculated for integer data by subtracting $0.5$ from lower class limits and adding $0.5$ to upper class limits.

Frequency Histogram

A graph that uses touching consecutive vertical bars to represent a frequency distribution, where the quantitative horizontal scale measures data entries and the vertical scale measures class frequencies.

Pareto Chart

A vertical bar graph in which the height of each bar represents frequency or relative frequency, positioned in order from highest to lowest.

Frequency Polygon

A line graph constructed by plotting points that represent the midpoint and frequency of each class and connecting the points in order from left to right with line segments.

Ogive

A cumulative frequency graph where the horizontal scale consists of upper class boundaries and the vertical scale measures cumulative frequencies, starting at the lower boundary of the first class with a cumulative frequency of $0$.

Sigma ($\Sigma$)

The uppercase Greek letter used in statistics to denote a summation, such as $\Sigma f$ representing the sum of all class frequencies.