Histograms and distributions

Frequency

the number of times a value of the data occurs

Frequency polygon

looks like a line graph but uses intervals to display ranges of large amounts of data

Frequency Table

A table for organizing a set of data that shows the number of times each item or number appears.

Histogram

a diagram consisting of rectangles whose area is proportional to the frequency of a variable and whose width is equal to the class interval.

Interval

also called a class interval; an interval represents a range of data and is used when displaying large data sets

Kurtosis

how flat or peaked a normal distribution is

Mode

The value that occurs most frequently in a given data set.

Multi-modal distribution

A distribution with more than one clearly discernible peaks. The peaks may be of the same frequency, or one may be the true mode while the others have very high (but not the highest) frequencies.

Negative skew

A curve or distribution of scores that has extreme scores below the mean that are atypical of the majority of scores.

Normal distribution

describes a symmetrical, bell shaped curve that shows the distribution of many physical and psychological attributes

Positive skew

tail to the right

Relative Frequency

A ratio that compares the frequency of each category to the total.

Skewed

a non-normal distribution