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Scatter Plots or Line of Best Fit Clipboard B Objective:To use scatter plots to write a line of best fit. Right click and click advance to advance slides!!

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Positive Correlation

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Negative Correlation

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No Correlation

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To find a line of best fit we must remember our answer might not be exact. We will choose two points in our scatter plot, the more you choose the more accurate the answer, so you may choose more. Use extreme points, points far apart. Place these points in your calculator, in stat. Then press the F1 key three times, substitute and you will have a line of best fit. You might have to look for the answer closest to yours.

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Example A 1. Pick 2 points (x, y) x is the first point go on the horizontal axis. y is the second point on the vertical axis. (1, 1) X-axis Y-axis (6, 7) 2. Go to stat on your calculator and type in your x values(1 and 6) under list 1 and your y values (1 and 7) under list 2. List 1 List 2 1 1 6 7 Press the F1 key 3 times Linear Reg a = 1.2 b = -.2 r=1 r^2 = 1 y = ax + b This following screen will appear Go to next Page Extreme points

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Linear Reg a = 1.2 b = -.2 r=1 r^2 = 1 y = ax + b Now we must substitute 1.2 and -.2 into the slope-intercept form. y = ax + b We must convert 1.2 into a fraction, go to menu---run, and type in 12, then press the a b/c button 10. The reason we use 10 is because there is one number to the right of the decimal. ( Two numbers we would use 100, three numbers we would use 1000 and so on. If the numbers repeats we use the number 9.) 12,10 1,1,5 After hitting exc you should get your fraction, improper in this case, because we have three number. If you have three numbers multiply the outsides and add the middle placing your answer over the last. 5 x 1 + 1 = 6/5 Next I will have to convert my b value again going to run and typing in -2 a b/c 10. This should give me the following -1/5. -2,10 - 1,5 Now I can substitute (1.2 became 6), my a value and (-.2 became 1/5), my b value into the equation y = ax + b.. My final answer is y = 6/5 x - 1/5 6/5 is my slope and -1/5 is my y intercept

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Example B 1. Pick 2 points (x, y) x is the first point go on the horizontal axis. y is the second point on the vertical axis. (6, 0)(0, 8)Make sure they are extreme points 2. Go to stat on your calculator and type in your x values(6 and 0) under list 1 and your y values (0 and 8) under list 2. List 1 List 2 6 0 0 8 Press the F1 key 3 times This following screen will appear Linear Reg a = -1.333333333 b = 8 r= -1 r^2 = 1 y = ax + b Go to next Page

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Linear Reg a = -1.333333333 b = 8 r= -1 r^2 = 1 y = ax + b Now we must substitute -1.3333333 and 8 into the slope-intercept form. y = ax + b We must convert 1.3333333 into a fraction, go to menu---run, and type in 3, then press the a b/c button 9. The reason we use 9 is because the number repeats itself 3333333. (If it did not repeat and it was only one number to the right of the decimal we would use 10. Two numbers we would use 100, three numbers we would use 1000 and so on. If the numbers repeats we use the number 9.) 3,9 1,3 Our answer is 1/3, but do not forget the -1 we left. So we have -1 1/3 multiply the 3 times the -1 and add the 1 you get 4 place this value over the 3. Your answer is -4/3 or youre a value. Next I will have to use my b value and substitute into the equation, there is no conversion since it is a whole number. Now I can substitute (-1.3333333 became -4/3), my a value and (8), my b value into the equation y = ax + b.. My final answer is y = -4/3 x + 8 -4/3 is my slope and 8 is my y intercept

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