Page 358 - Statistics for Dummies

342
Part VI: The Part of Tens
✓ Labels keep your mind organized. You are less likely to get buried in
calculations and forget what you’re doing if your work involves symbols
and not just numbers. By sorting out the information you are given,
you’re less likely to resort to reading the problem over and over again,
raising your anxiety level each time.
✓ You use the labels to figure out which formula or technique you need
to use to solve a problem. For example, if you think you need a hypoth-
esis test but no claim is made about the population mean, hold up.
You may need a confidence interval instead; this realization saves you
precious time because you won’t be spinning your wheels in the wrong
direction. Labels help you quickly narrow down your options.
✓ Labeling helps you resist the urge to just write down numbers and
push them around on the paper. More often than not, number-pushing
leads to wrong answers and less (if any) partial credit if your answer
is wrong. Your professor may not be able to follow you, or just doesn’t
want to spend all that time trying to figure it out (sorry to say, but this
happens sometimes).
Labeling saves you anxiety, time, and points when you take your exam. But
in order to be successful on exam day, you need to start this practice early
on, while the problems are easy to do. Don’t expect to suddenly be able to
sort out the information on exam day if you never did it before; it’s not gonna
happen. Make it your habit right away and you won’t freak out when you see
a new problem. You’ll at least be able to break it down into smaller chunks,
which always helps.
Draw a Picture
You’ve heard the expression “A picture is worth a thousand words.” As a
statistics professor, I say, “A picture is worth a thousand points (or at least
half the points on a given problem).” When the given information and/or the
question being asked can be expressed in a picture form, you should do it.
Here’s why:
✓ A picture can help you see what’s going on in the problem. For exam-
ple, if you know exam scores have a normal distribution with mean 75
and standard deviation 5 (see Chapter 9 for more about normal distribu-
tion), you draw a bell-shaped curve, marking off the mean in the center
and three standard deviations on each side. You can now visualize the
scenario you’re dealing with.
✓ You can use the drawing to help figure out what you are trying to find.
For example, if you need to know the probability that Bob scored more
than 70 points on the exam, you shade in the area to the right of 70 on
your drawing, and you’re on your way.

3/25/11 8:12 PM
30_9780470911082-ch21.indd 342
30_9780470911082-ch21.indd 342 3/25/11 8:12 PM