 Consider the variables family income and family expenditure.  Increase & decrease together  Change in one variable is accompanied by change in the other variable  Price and demand of a commodity are related variables  When Price increases, demand decreases and vice versa

 If the change in one variable is accompanied by a change in the other, then the variables are said to be correlated.  Family Income & Family Expenditure are correlated  Price and Demand are correlated

 Correlation can tell you about the relationship between variables. It is used to understand:  Whether the relationship is positive or negative  The strength of the relationship  In the case of family income & expenditure, they both increase and decrease together, so this is a positive correlation  In the case of price and demand, if one increases, the other decreases, so this is a negative correlation

 A “variable” is an attribute that can be measured  One-variable data has measures for one attribute  Recognize them when you see:  Bar Graphs  Circle Graphs  Tally Charts  One-variable data can be measured using:  Mean, Median, Mode  These are “Measures of Central Tendency”

 Measures for 2 attributes  Recognize them when you see  Table of Values  Ordered Pairs  Scatter Plots  Two-variable data can be analyzed by looking for a trend or pattern in the relationship.  This trend may be:  Linear  Quadratic  Exponential

Blood TypesPercent of People A43% B8% AB3% O46% Choose a type of graph to represent the data. Describe as one-variable or two-variable data. One Variable Data on a Pie Chart

Choose a type of graph to represent the data. Describe as one-variable or two-variable data. Instructional Hours Driving Test Score 1078% 1585% 2196% 675% 1884% 2045% 1282% Two-Variable Data on a Scatter Plot

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