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[RC] Probably Not (was: Las Cruces, etc.) - k s swigart

Dawn Carrie said in comparing the completion rate of less than 30% for
the FEI riders on the same course:


Interestingly, the 5 non-FEI riders had an 80%
completion rate.  Something to think about?


However, to answer her question, because the sample size is so small,
the difference between the completion rates of the FEI riders and the
non-FEI riders is probably not statistically significant.

When I did a comparison of two years worth of statisitics (instead of
just one small ride) where there were both FEI riders and non-FEI riders
at the same rides, the completion rates for both groups came out to be
about the same...about 60%, like it is for all 100 mile rides that the
AERC has stats for.

I asked the same question about 6 months ago when the completion rate of
FEI riders at Ft. Howes was so much lower than that of the non-FEI
riders, but investigation of a larger sample size did not bear out any
such difference.

The difference in the ride this week in New Mexico can most likely be
attributed to random chance.

Somebody with access to the actual statistics and their variability
could actually do the math to determine whether the difference is
statistically significant, but I am willing to bet that it is not...even
though on the face of it, the difference seems huge.

When dealing with small sample sizes, little differences can seem huge
because just one rider can make such a huge difference in the
percentages (e.g. only one more than the average number of riders
completing finished the non-FEI portion of the ride, yet this one rider
made the completion rate for the non-AERC portion of the ride appear
huge).

kat
Orange County, Calif.
:)




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