Question 656178
  <pre><font face = "Tohoma" size = 3 color = "indigo"><b> 
Hi,
Don't know what You have been using to determine  <u>standard deviation</u>etc in general:
If you have a TI 83 calculator,might recommend this tutorial site:
http://www.tc3.edu/instruct/sbrown/ti83/regress.htm
{{{r[xy]=s[xy]/s[x]s[y]}}} where 
s[x]= sqrt{{{(sum((x[i]-m[x])^2)/(n-1))}}} and s[y] = sqrt{{{(sum((y[i]-m[y])^2)/(n-1))}}}
and {{{s[xy] = (sum((x[i]-m[x])(y[i]-m[y]))/(n-1))}}} 
In the normal Work Up using an Excel Worksheet, there is a need to sum (xi - 2.5)(yi - 78.2) as well 
       (xi-2.5)^2 (yi-78.2)^2 (xi-2.5)(yi-78.2)
	6.25	475.24	-54.5
	2.25	190.44	-20.7
	0.25	14.44	-1.9
	0.25	0.04	-0.1
	2.25	148.84	-18.3
	6.25	739.84	-68
Sum	17.5	1568.84	-163.5
     {{{s[x] =1.87}}} {{{ s[y] =17.71}}} {{{s[xy] =  -32.7}}}
		33.14	
{{{r = -32.7/(1.87*17.71)}}} = -32.7/33.14 = -.9867
Regression Line 1s:  y = ax + b,  where
a ={{{sum((x[i]-m[x])(y[i]-m[y]))/sum((x[i]-m[x])^2)}}}  
 and {{{b = m[y] -  a*m[x]}}}
a = -163.5/17.5 = -9.34
{{{b = 78.2 - (-9.34*2.5)}}} = 100.5
y = -9.34x + 100.5