Exploring Data with Tables and Graphs: Frequency Distributions

Vocabulary flashcards covering key concepts, definitions, and formulas from the lecture on frequency distributions and data visualization.

Frequency Distribution

Shows how data are partitioned among several categories (or classes) by listing the categories along with the number (frequency) of data values in each of them.

Lower class limits

The smallest numbers that can belong to each of the different classes.

Upper class limits

The largest numbers that can belong to each of the different classes.

Class boundaries

The numbers used to separate the classes, but without the gaps created by class limits.

Class midpoints

The values in the middle of the classes, which can be found by adding the lower class limit to the upper class limit and dividing the sum by 2.

Class width

The difference between two consecutive lower class limits (or two consecutive lower class boundaries) in a frequency distribution.

Class width formula

The formula used to estimate class width: $\text{Class width} \approx \frac{\text{maximum data value} - \text{minimum data value}}{\text{number of classes}}$

Relative Frequency Distribution

A frequency distribution in which each class frequency is replaced by a relative frequency (or proportion) or a percentage.

Relative frequency formula

The ratio used to calculate relative frequency: $\text{Relative frequency for a class} \approx \frac{\text{frequency for a class}}{\text{sum of all frequencies}}$

Percentage for a class formula

The formula used to compute class percentages: $\text{Percentage for a class} \approx \frac{\text{frequency for a class}}{\text{sum of all frequencies}} \times 100\%$

Cumulative Frequency Distribution

A frequency distribution in which the frequency for each class is the sum of the frequencies for that class and all previous classes.

Normal Distribution (Frequency Distribution Criteria)

A distribution where frequencies start low, increase to one or two high frequencies, decrease to a low frequency, and are approximately symmetric.

Gaps in data

The presence of empty classes in a frequency distribution, which can indicate that the data are collected from two or more different populations.

Histogram

A graph used for summarizing and investigating the distribution of data that is easier to interpret than a table of numbers.