Croxton and Cowden

Statistics  

“Statistics may be defined as the collection, presentation, analysis, and interpretation of numerical data.”

Central Value (tendency)

“An average is a single value within the range of data that is used to represent all values in the series. Since an average is somewhere within the range of the data, it is also called a measure of Central Value

Mode 

“The mode may be regarded as the most typical of a series of value”

Correlation 

“When the relationship is of a quantitative nature, the approximate statistical tool for discovering and measuring the relationship and expressing it in a brief formula is known as correlation.”

 Index numbers

“Index numbers are devices for measuring differences in the magnitude of a group of related variables.”

Skewness

“When a series is not symmetrical, it is said to be asymmetrical, or skewed.”