Re: [libreoffice-users] intercept and slope -- is there a problem?

On 2012-06-15 12:47, Robert Peirce wrote:
> If I use a small amount (3 pairs) of dummy information, the intercept,
> slope and R^2 are exactly what I expect them to be.  If I use something
> on the order of 400 pairs it makes no sense at all.  When I use Linest,
> the results are reasonable.
>
> I am evaluating stock trading systems against holding the market.  The
> data pairs are the monthly percentage change in the model vs. the
> market.  A regression produces the y-intercept (called alpha), the slope
> (called beta) and R^2.
>
> Generally, if I know the total return for the model and the market the
> calculation
>
>     "total model return" = "total market return" * beta + alpha
>        or
>     y = mx + b
>
> is fairly close if I get the results from linest.  They are way off from
> intercept and slope.
>
> If the dependent variable is in A and the independent in B and there are
> 400 pairs, I can use INTERCEPT|SLOPE(A1:A400; B1:B400).  The results
> aren't even close and I don't know why.  Plugging the average returns
> for the market into the equation to calculate the expected return for
> the model produces nothing reasonable.
>
> Any ideas?  I am probably missing something really obvious.
Hi.
I filled a column X with =RAND()*500 and a column Y with =B476*2+RAND()*2+5
Column B is the X values. The slope looks about right as does the 
intercept (keep refreshing with F9). I created a chart and added the 
trend line and the trend line matches the functions SLOPE and INTERCEPT.
R squared is 0.999

Opensuse LO 3.4.5

Cheers,
Steve

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