CH. 2: Frequency Distributions

Frequency Distribution

a frequency distribution is an organized tabulation of the number of individuals located in each category on the scale of measurement

Percentile Rank

the percentile rank of a particular score is defined as the percentage of individuals in the distribution with scores at or below the particular value

Percentile

when a score is identified by its percentile rank, the score is called a percentile

Frequnecy Distribution Table

a table that organizes data values and shows how often each (frequnecy) occurs in a dataset

Proportion (p)

a measure that expresses the frequency of a category divded by the total number of cases in the dataset

Percentage

a proportion multiplied by 100

Cumlative Frequency (f)

the total number of observations that fall at or below a given value in a frequency distribution

Cumulative Percentages (c%)

the percentage of observations that fall at or below a given value in a frequnecy distribution

Range

the difference between the highest and lowest scores in a dataset

Grounded Frequency Distribution

a frequency table where socres are grouped into intervals instead of listing every value individually

Class Interval

a group or range of values used in a grouped frequency distribution

Apparent Limits

the upper and lower values listed in a class interval, which may not include all possible exact values (e.g., 10-14 actually covers 9.5 up to 14.5)

Histogram

a graph showing frequencies for continuous data using adjacent bars

Polygon

a graph showing frequencies with points plotted above each score or interval and connected by straight lines

Bar Graph

a graph showing frequnecies for discrete or categorical data using separate, non-touching bars

Relative Freqency

the proportion or percentage of times a value occurs relative to the total number of observations

Normal Distribution

a symmetrical, bell-shaped distribution where most scores cluster around the mean

Symmetrical Distribution

a distribution where the left and right sides are mirror images

Skewed Distribution

a distribution where socres pile up on one side and taper off on the other

Tail(s) of a Distribution

the ends of the distribution where extreme values occur

Positively Skewed Distribution

a distribution with a tail extending to the right (toward the higher values)

Negatively Skewed Distribution

a distribution with a tail extending to the left (toward lower values)

Stem and Leaf Display

a method of organizing data that shows the actual numbers by splitting each value into a “stem” (leading digit) and a “leaf” (trailing digit)