| Price charged (x) | 350 | 450 | 600 | 800 | 1000 |
| Number sold (y) | 2500 | 1450 | 800 | 1100 | 100 |
Write the equation for line of best fit.
I have tried this about 3 times yet I keep getting the wrong answer. I know the answer is y = -2.96x + 3085.74 but I keep getting answers like y = -10.5x + 26600. What step am I missing or what am I doing wrong? I know I'm missing something but I just don't know what. Please help and maybe show how to get the correct answer because I'm lost. Thank you in advance.
+128408 Here's the procedure....hang on....there are a few steps here
Take the mean of the x values = 640
Take the mean of the y values = 1190
Calculate the difference between each x value and the mean of the x values and do the same for the y values
350 - 640 = -290 2500 - 1190 = 1310
450 - 640 = -190 1450 - 1190 = 260
600 - 640 = -40 800 - 1190 = -390
800 - 640 = 160 1100 - 1190 = -90
1000 - 640 = 360 100 - 1190 = -1090
Take the products of these results and add them
(-290)(1310) + (-190)(260) + (-40)(-390) + (160)(-90) + (360)(-1090) = -820500 (1)
Square each value in the first column above and add them together =
(-290)^2 + (-190)^2 + (-40)^2 + (160)^2 + (360)^2 = 277000 (2)
The slope of the line = (1) / (2) = - 2.96
The y intercept (b) is found as
b = average of y values - (slope * average of x values)
b = 1190 - ( [-820500/277000] * 640) = 3085. 74
So....our line is
y = -2.96x + 3085.74
