I need help ... How to write an equation of a trend line ?

Question

jdoe0001 · Answer

take a quick screenshot of it and post it here

anonymous · Answer

(-10, 3) (-5,1) (-1,-4) (3,-7) (12, -12)

amistre64 · Answer

$$Y=\frac{n\sum xy-\sum x\sum y}{n\sum xx-\sum x\sum x}(X-\bar X)+\bar Y$$

amistre64 · Answer

or, if you have a ti83 ...

list1 = x parts
list2 = y parts

2nd, stat, LineReg L1,L2

amistre64 · Answer

no 2nd,  just stat, linereg

anonymous · Answer

I don't get it -.-

amistre64 · Answer

it is labor intensive by hand ... an excel sheet helps

anonymous · Answer

Oh my god I feel dumb

amistre64 · Answer

how are you spose to address this; by hand, by calculator, or by excel?

anonymous · Answer

By hand

amistre64 · Answer

by hand will not be productive; but we can organize the data similar to an excel sheet

anonymous · Answer

I just need to understand how to do it

amistre64 · Answer

stack the points, and multiply xy to the right of it;  put x^2 to the left of it

you will need to work with these columns

amistre64 · Answer

you need to organize something like this

amistre64 · Answer

the rest is just plugging into the equation

anonymous · Answer

Okay ...

amistre64 · Answer

the hardest thing is the slope, it has the most parts


n(sum xy) - sum x(sum y)
----------------------
n(sum xx) - sum x(sum x)



5(-196) - (-1)(-19)
------------------
   5(279) - (-1)(-1)

amistre64 · Answer

- 999
 ------
  1394

which may or maynot reduce :)

amistre64 · Answer

take the average x and average y to build a point slope equation with:
$$y=m(x-avgX)+avgY$$
and that is the trendline equation

amistre64 · Answer

$$y = -\frac{999}{1394}(x+.2)-3.8$$

amistre64 · Answer

excel has a trendline feature, and it agrees with this process :)