This may be a bit pedantic, but you have confused "quartiles" with "quantiles", and there should be only 3 meaningful quartiles (the help text lists 0-4 as possible quartile values).
0th quartile is not really meaningful empirically (it would be the lowest value observed), and similar things can be said about the 4th quartile (it is the highest value observed).
In general, there are N-1 meaningful N-quantiles. The percentiles are the 100 quantiles, quartiles are the 4 quantiles, and the median is the only 2 quantile.
nferraz
commented
11 years ago
This may be a bit pedantic, but you have confused "quartiles" with "quantiles", and there should be only 3 meaningful quartiles (the help text lists 0-4 as possible quartile values).
0th quartile is not really meaningful empirically (it would be the lowest value observed), and similar things can be said about the 4th quartile (it is the highest value observed).
In general, there are N-1 meaningful N-quantiles. The percentiles are the 100 quantiles, quartiles are the 4 quantiles, and the median is the only 2 quantile.