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## Dependent Variable (placed on vertical axis: y)

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**Dependent Variable(placed on vertical axis: y)**• A dependent variable is a variable dependent on the value of another variable Independent Variable(placed on horizontal axis: x) • The independent variable causes an apparent change in, or affects the dependent variable**Examples:**• In a call centre, the number of customers serviced depends on the number of agents • At ski resort, the amount of sales, in $, depends on the amount of snow • The amount of bacteria on your hands depends on how often frequently you use hand sanitizer. dependent variable (y) independent variable (x)**positive**negative no**Strong or Weak Correlation?**If the points nearly form a line, then the correlation is ___________________. If the points are dispersed more widely, but still form a rough line, then the correlation is _______________________. strong weak**Does age have a strong positive correlation with height?**Explain. • Do you think the variables are placed appropriately on the axes? • c) Would weight vs. age show a strong positive correlation? • d) Can you think of a variable that does have a strong positive correlation with age? • e) Can you think of a variable that has a strong negative correlation with age?**Line of**Best Fit …affectionately known as LOBF**All about the LOBF…**• shows a trend or pattern on a scatterplot • used to make predictions How do I draw it? What is it? • models the trend/pattern • models the trend/pattern • through as many points as possible • equal points above and below the line**Line of Best Fit**To be able to make predictions, we need to model the data with a line or a curve of best fit. Guide for drawing a line of best fit: 1. The line must follow the ______________. 2. The line should __________ through as many points as possible. 3. There should be ____________________________ of points above and below the line. 4. The line should pass through points all along the line, not just at the ends. trend pass equal**#2**#1 #4 #3 And what is wrong with the others? Line not in middle of points Which one of these is the best LOBF? Doesn’t model trend Wrong for all kinds of reasons!**Return to front side of hand out and make lines of best fit**on each of the given 6 graphs.**You can use LOBF’s to make predictions for values that are**not actually recorded or plotted. Extrapolation Interpolation • prediction involving a point outside the set of data • prediction involving a point within the set of data (line needs to be extended)**Extend the line!**Is this interpolation or extrapolation? How tall would a person be that had a humerus of 44 cm? 181 cm tall Using our height and humerus data… exptrapolation**Is this interpolation or extrapolation?**How long would a person’s humerus be that was 163 cm tall? 28 cm long Using our height and humerus data… interpolation**Makin’ sure you get it!**See bottom of handout