I found the expected value for the number of boys for a family with five children to be 2.5. I must have made an error because a family with 2.5 boys cannot occur

We are meant to round down fractions of persons to the nearest whole number possible

Step-by-step explanation:

Here we have the question with regards the result of a fraction of a person to a solution of a statistic question.

Where the result is a fraction, the format is, since most solutions to questions in statistics with regards to people pertain to the maximum amount of persons that fit a class, and since it is not technically feasible to account for the next half of the person after getting your result, we have to put down only the number of whole people possible which means as a rule we always round down the decimal or fractions to the nearest whole number of person

Therefore, you are correct, only that we can put 2 instead of 2.5 as your answer.