• there is a correlation between the variables amount
• scatter diagrams - is a graph in which each point represents the values of two variables
• suppose there really were a gene that made people prone to both smoking and lung cancer. Explain why we would still find a strong correlation between smoking and lung cancer 
• we assign one variable to each axis and label the axis with values that comfortably fit all the data.
• Thanks to a large bonus at work, you have a budget of $6,000 for a diamond ring. 
• types of correlation- positive correlation, 
• positive correlation - both variables tend to increase ( or decrease ) together  
• negative correlation - the two variables tend to change in opposite directions, with one increasing while the other decreases. 
• No correlation - there is no apparent ( linear) relationship between the two variables
• nonlinear correlation - the two variables are related but the relationship results in a scatter diagram that does not follow a straight-line pattern
• test next Thursday
• statisticians measure the strength of a correlation with a number called te correlation coefficent, represented by the letter r. 
• properties of the correlation coefficent 
• the correlation,r, is a measure of the strength 
• if there is a negative correlation, the correlation coefficient is negtive (-1<r<0): When one variable increases, 
• 7.1 - 1,2,3,4,11,17,19