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Correlation Correlation When two sets of data are strongly linked together we say they have a High Correlation. The word Correlation is made of Co- (meaning "together"), and Relation Correlation is Positive when the values increase together, and Correlation is Negative when one value decreases as the other increases Like this: Correlation can have a value:
Normal Distribution Data can be "distributed" (spread out) in different ways. But there are many cases where the data tends to be around a central value with no bias left or right, and it gets close to a "Normal Distribution" like this: A Normal Distribution Normal Distribution

Standard Deviation and Variance

Standard Deviation and Variance Deviation just means how far from the normal Standard Deviation The Standard Deviation is a measure of how spread out numbers are. Its symbol is σ (the greek letter sigma)
Quartiles Quartiles Quartiles are the values that divide a list of numbers into quarters. First put the list of numbers in order Then cut the list into four equal parts The Quartiles are at the "cuts" Like this: Example: 5, 8, 4, 4, 6, 3, 8 Put them in order: 3, 4, 4, 5, 6, 8, 8 Cut the list into quarters:
Calculating the mean from a frequency table Calculating the mean from a frequency table It is easy to calculate the Mean: Add up all the numbers, then divide by how many numbers there are. Example 1: What is the Mean of these numbers?
Standard Deviation Formulas Deviation just means how far from the normal Standard Deviation The Standard Deviation is a measure of how spread out numbers are. Standard Deviation Formulas