Scientists mostly gain new knowledge through direct observation and applying the scientific method. They would start with a hypothesis and test it, then change it or confirm it. Others would test their confirmation from one point, while the third group would test what the second said. And so on and so forth.
There are two possibilities: The offspring can either be HH or Hh; therefore, there is a 50% chance of the offspring being one of the two above. This means that there is a 50% chance off the offspring being tall or short.