There must have been something common to all alcohols right? Like constant volume, mass, moles... Seeing as they all were under the same conditions and you have nothing else to distinguish them by.
If you walked into the demo late you may have missed that part!
Or maybe your teacher deliberately kept this a secret and just wants you to calculate each rate relative to the other alcohols? For example, if you had alcohols A-E, which took 16, 60, 22, 7, 34 (minutes) respectively to evaporate, you can express them as ratios of one another. For example, take B (or whichever) and you can say: the rate of A is 60/16 times that of B, rate of C is 60/22 times that of B, etc...
Seems likely he will later give you the identity of each alcohol, and compare how their structures and size affect their boiling point.