Page 361 - Statistics for Dummies

Chapter 21: Ten Surefire Exam Score Boosters
big red circle around one of his answers, which happens to be the number 2.
Why was writing the number 2 for an answer such a problem? Because the
question asked him to find a probability, and probabilities are always between
0 and 1. As a result, he didn’t get any points for that problem, not even partial
credit. In fact, I’ll bet his professor wanted to give him negative points for
making such a mistake. (They really don’t like it when you totally miss the
boat.)
Always take the time to check your final answer to see if it makes sense. A neg-
ative standard deviation, a probability more than 1, or a correlation of –121.23
is not going to go over well with your professor, and it will not be treated like
a simple math error. It will be treated as a fundamental error in not knowing
(or perhaps caring) what the result should look like.
If you know an answer you got can’t possibly be right, but you cannot for the

life of you figure out where you went wrong, don’t waste any more time on it.
Just write a note in the margin that says you know your answer can’t be right
but you can’t figure out your error. This helps separate you from the regular Joe 345
who found a probability of 10,524.31 (yes, I’ve seen it) and merrily moved on.
By the way, you may be wondering why this world-class statistician still
keeps this exam page framed on his office wall. He says it’s to keep him
humble. Learn from his example and never move on to the next problem
without stepping back and saying “does this answer even make sense?”

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