Unfortunately the sentence is grammatically correct (except that it should say
aquellos de pie **y** aquellos sentados). I say this because it is extremely tangled; the English source must be just as ugly!
As belisarius commented,
bien sea is used here in the sense of
either It would be more natural to use
o bien. Let's untangle the mess. Depending on the data, one of two scenarios is valid:
- It is possible to show that, in average, standing does not increase pulse rate.
- It is possible to estimate the difference in pulse rate between standing and seating subjects.
(Notice that the Spanish sentence is well constructed in that it uses "es posible" outside the disjunction.)
Part of the problem with the sentence is that it is an empty statement. Obviously the pulse rates data will be the same for standing and seating subjects, or not. In one case we show it is invariant, in the other case we measure the discrepancy... D'oh!
Here is an alternative way to say the same in Spanish.
Si los datos no muestran un mayor pulso promedio en individuos de pie, entonces permitirán estimar la diferencia entre el pulso promedio de sujetos sentados y de pie.