Re: BP Ultimate--worth it?
- From: Steve Walker <steve@xxxxxxxxxxxxxxxxxxx>
- Date: Mon, 23 Apr 2007 18:04:21 +0100
In message <1177340839.366422.206840@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
Mathew Newton <usenet@xxxxxxxxxxxxxxx> writes
Anyway, the range is around 4-5mpg and it goes up and down like
nobody's business. Hence, unless I get over this amount then any
improvement will be just lost in the noise...
I calculated a moving % Optimax for each fill and then calculated the
Kendall correlation coefficient between mpg and % Optimax. Probably not
a suitable approach for the way you've done it, as you've fuelled it in
blocks.
You could use a Mann-Whitney U-test to compare medians between groups
(I'd still go for a non-parametric test on the grounds that it's more
conservative and that the frequency distribution is probably not normal)
Just eyeballing the data, if you sort your columns by mpg, you will see
that the lowest third of mpgs are exclusively 95RON, with the Optimax/V-
Power all in the top 2/3.
I get U=1246 for N1,N2 = (121,28). Using a normal approximation, that
gives Z = -2.18, which would be significant. However, because of the way
that you've used the different fuels, there's no way of saying whether
that's because of the age of the engine or the time of year or changes
in the way that you drive.
--
Steve Walker
.
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