Those hypotheses that do pan out are kept and become part of the knowledge base of science. Another part of hypothesis testing consists of investigating whether your observations and subsequent hypotheses apply to populations. Z scores Recall the discussion above about measures of central tendency and variability. In descriptive statistics these two measures are used to describe a particular distribution. However, with two or more distributions, you need to worry about whether or not the distributions are the same or different.
Z scores transform the distributions in question to the same standard scores.
In fact, Z scores are often called standard scores. However, Z scores may be mathematically transformed into equivalent distributions. One example of such a transformation uses a mean of 50, and a standard deviation of 10. Many other such transformations exist. College entrance tests are good examples.