bellshaped curve

A common type of histogram characterized by a high center, tapered sides, and bellflared edges. A bellshaped curve reflects conditions that exhibit natural variation.

data

A collection of numbers or facts that is used as a basis for making conclusions.

fraction

A numerical expression representing a part of a larger whole. A fraction can be converted to a decimal by dividing the upper number, or numerator, by the lower number, or denominator.

histogram

A visual graph that shows the frequency of a range of variables.

horizontal scale

The portion of a histogram that lists the range of variables.

mean

The average of a numerical set. It is found by dividing the sum of a set of numbers by the number of members in the group.

median

The value of a numerical set that equally divides the number of values that are larger and smaller. For example, in a set containing nine numbers, the median would be the fifth number.

mode

The value of a numerical set that appears with the greatest frequency.

natural variation

Variation resulting from sources that are normal and expected. Natural variation is predictable over time.

percentage

A numerical expression that includes a percent sign, with 100 assumed as the denominator.

population mean

The mean of a numerical set that includes all the numbers within the entire group.

probability

The likelihood that a particular event will happen in the future. Probability can be expressed as a fraction, ratio, or percentage.

process

A set of activities that uses resources to transform inputs into outputs. Essentially, a process describes the way "things get done."

random sampling

The process of collecting and analyzing only a small representative portion of a larger group. Each item must have the same likelihood of being selected.

range

The difference between the smallest and the largest values within a numerical set.

ratio

A numerical expression representing a part of a larger whole or proportion. A ratio consists of two numbers separated by a colon.

sample mean

A mean of a numerical set that includes an average of only a portion of the numbers within a group.

standard deviation

A number representing the degree of variation within a numerical set.

statistics

The science of collecting, summarizing, and analyzing numerical data. Statistics makes it possible to predict the likelihood of events.

unnatural variation

Variation resulting from one or more sources that involve a fundamental change in a process. Unnatural variation is undesirable.

variation

A difference between two or more similar things.

vertical scale

The portion of a histogram that indicates the frequency of each variable.
