When analysing data or entries it is necessary to determine their expected outcome before recording them True of false and why?

It is neither true nor false.

It is important that you have a view about the expected outcomes so that you can test whether or not the assumptions for the model - independent, identically distributed errors - is valid or not. While these are based on the differences between the expected and observed outcomes, it is not necessary to determine the expected outcomes beforehand. Determining their distribution is sufficient.