Ch 2: Frequency Distributions and Graphs

A set of vocabulary flashcards covering key concepts from frequency distributions, grouping data, interval concepts, proficiency levels, and basic graph types.

Frequency distribution

A summary showing how often each value or interval occurs in a dataset.

Simple frequency distribution

A basic frequency distribution that lists individual scores and their frequencies.

Grouped data (grouped frequency distribution)

A frequency distribution that summarizes data into intervals to clarify patterns in large datasets.

Real range

One more than the difference between the largest and smallest values in the dataset (max − min + 1).

Interval width

The size of each group interval; Interval width = Real range ÷ Number of intervals (rounded to the nearest whole number).

Upper bound

The highest value included in an interval.

Lower bound

The lowest value included in an interval.

Interval

A range of scores with defined lower and upper bounds used in grouped data.

Non-overlapping intervals

Intervals that do not share any scores; every score falls into one interval only.

Equal interval widths

Intervals that all have the same width (size).

Proficiency Levels

A predefined set of categories used to classify performance levels in standardized tests (e.g., Below Basic, Basic, Proficient, Advanced).

Below Basic

Proficiency category for scores in the range 300–416.

Basic

Proficiency category for scores in the range 417–437.

Proficient

Proficiency category for scores in the range 438–460.

Advanced

Proficiency category for scores in the range 461–550.

Cumulative frequency distribution

A distribution showing the total number of observations at or below each value.

Relative frequency distribution

A distribution showing the proportion (0 to 1) of observations in each interval.

Relative frequency

The frequency of an interval divided by the total number of observations (N), a value between 0 and 1.

Relative percent distribution

A relative frequency expressed as a percentage (0–100%).

Histogram

A graph with rectangular bars showing frequencies for quantitative intervals; bars touch to indicate continuous data.

Frequency polygon

A graph formed by plotting the midpoints of histogram intervals and connecting the dots with lines.

Bar chart

A graph used for categorical or ordinal data; bars do not touch.

Pie chart

A circular chart showing proportions of categories as wedges; slice degrees are proportional to percentages (degrees = percentage × 3.6).

Misleading graphs

Graphs that distort data or misrepresent relationships to mislead viewers.

Independent variable (IV)

The variable manipulated or categorized to observe its effect on the dependent variable.

Dependent variable (DV)

The variable measured to assess the effect of the IV.

Scale (nominal/ordinal/interval/ratio)

Levels of measurement: nominal (categories), ordinal (ordered), interval (equal units, no true zero), ratio (equal units with true zero).

Units of measurement

The units used to express the value of a variable (e.g., points, percent, degrees).

Levels for the IV

The distinct categories or values that the independent variable may take (e.g., control vs. experimental).