1. Get Ready for the AP Exam

2. Before the AP Exam
Be able to describe a distribution of data (center, shape and spread)
Be able to calculate 5-number summary, IQR and outliers
Be able to draw boxplot, histogram, etc…know when to use which one.
Know how to read generic computer output.

3. Before the AP Exam
Know the difference between a scatter plot and a residual plot.
Know that a model that produces predicted values isn't providing actual data values. If the equation for a least-square regression line is y = 1.5x , then the slope and y-intercept need to be interpreted properly. For instance, one might say that "on the average, a unit change in x results in a change of 1.5 units in y" and that "the predicted value of y is 3.34 when x = 0."

4. Before the AP Exam
Know correlation coefficient and coefficient of determination & be able to interpret in context.
Don't confuse coefficient of correlation and slope of least-squares regression line.
A slope close to 1 or -1 doesn't mean strong correlation.
An r value close to 1 or -1 doesn't mean slope of least-squares regression line is close to 1 or -1.
Relation between b (slope of regression line) and r (coefficient of correlation) is b = r(Sy/Sx). This is on formula sheet provided for the exam.
Remember that r2 > 0 doesn't mean r > 0. For instance, if r2 = 0.81, then r = 0.9 or r = -0.9.

5. Before the AP Exam
Remember that the least-squares regression line contains the point (mean x, mean y), where mean x is the mean of the x-values, and mean y is the mean of the y-values.
A coefficient of correlation near 0 doesn't necessarily mean there are no meaningful relationships to be observed between the two data sets. Whenever possible, look at the "shape" of the data.
Realize that logarithmic transformations can be practical and useful. Among other things, taking logs cuts down the magnitude of numbers. Also, if {(x,y)} has an exponential pattern, then {(x,log y)} has a linear pattern.

6. Before the AP Exam Know the formulas and be able to write them out!
Know Simpson’s Paradox: The effects of lurking variables can change or even reverse relationships between 2 categorical variables. This can result when data from several groups are combined to form a single group.
Binomial vs Geometric
Discrete Random Variable
Central Limit Theorem
Law of Large Numbers

7. Before the AP Exam
Know the different inference tests and be able to conduct a significance test and confidence interval in the appropriate situation.
Only pool for 2-sample z proportions
Know that the null and alternate hypotheses are stated in terms of population parameters, not sample statistics.
Know the different assumptions and formulas for the different inference tests
Know Type I, Type II, and Power ** Type II and Power are z-score concepts

8. Before the AP Exam Adjust width of confidence interval
Standard deviation vs Variance

9. Before the AP Exam
Know the difference between an observation and an experiment
Understand the difference between a simple random sample and the random assignment of treatment to subjects.
Understand that there are two types of replication in experiments: (1) Replication within the experiment quantifies variablility within the experiment, and (2) replication of the experiment helps achieve validation.
Understand terms like confounding, lurking variables, etc.
Know different types of sampling.
Know different types of experimental design

10. Before the AP Exam
Be careful with the concept of simple random sample (SRS).
If each individual in a group has an equal probability of being chosen in a sample, it doesn't follow that the sample is an SRS.
Example: Consider a class of 6 boys and 6 girls. I want to randomly pick a committee of two students from this group. I decide to flip a coin. If "heads," I will choose two girls by a random process. If "tails," I will choose two boys by a random process. Now, each student has an equal probability (1/6) of being chosen for the committee. However, the chosen two students do not represent an SRS of size two picked from members of the class, for the selection process does not allow for a committee consisting of one boy and one girl. To have an SRS of size two from this class of 6 boys and 6 girls, each committee of two students would have to have an equal probability of being chosen.

11. Multiple Choice Questions
You don't have to answer all of the questions to get a good overall score.
If an answer is "obvious," think about it. If it's so obvious to you, it's probably obvious to others... and the chances are good that it is not the correct response. For example, suppose one set of test scores has a mean of 80, and another set of scores on the same test has a mean of 90. If the two sets are combined, what is the mean of the combined scores. The "obvious" answer is 85 (and will certainly appear among the answer choices), but you, as an intelligent statistics student, realize that 85 is not necessarily the correct response.

12. Multiple Choice Questions
If a question and/or answer choice set appears to be detailed and you need to do a lot of reading to reach a conclusion, most of the answer choices will probably be obviously incorrect. Don't be frightened off by questions and/or answer set choices that seem to be wordy. Just read carefully, and use the highlighting technique previously mentioned.

13. AP Free Response Questions
Read a problem carefully, sentence by sentence.
Relate to the problem. Decide what statistical concept/idea is involved. This will allow you to make an intelligent approach to questions asked. If you get started on an intelligent path, you will probably get some points even if you make some mistakes along the way.

14. AP Free Response Questions
Be neat, Make it clear to the reader what you are attempting to do. However, don't write too much. Overkill can waste valuable time. And if you contradict yourself, will count against you.
Questions may well look very detailed. You may be given much more information than you actually need. This is likely to be true if you are shown a computer printout. Don't get flustered by the way a problem "looks" when you first glance at it. * Some questions may give you considerable leeway in choosing an approach to a solution. Consider your options carefully and take the one that requires the least amount of time.

15. AP Free Response Questions
Don't be calculator-inefficient. It is certainly possible to waste time punching numbers into a calculator. Entering lists of numbers into a calculator can be time-consuming, and certainly doesn't represent a display of statistical intelligence. If, upon reading an AP question, you think you will have to enter many numbers into a calculator, you are probably overlooking something. Reread the problem, and look for a quicker path to a solution.

16. Just Before Exam Day The night before get plenty of sleep!
You are done studying 2 nights before your AP Exam. Look over your notes the night before (briefly)!
Make sure you pack your calculator with working batteries, extra batteries and pencils/erasers the night before. Bring a backup calculator if necessary.

17. AP Exam – The Big Day
Relax, and think. Remember that everyone else taking the exam is in a situation identical to yours. Realize that the problems will probably look detailed compared to problems you have encountered in other math courses.
Pace Yourself.
Multiple Choice – skip problems, mark them and come back. Guess an answer if narrow down to 3 choices.
Free Response – do problem 1 then problem 6 then the rest in order of difficulty.

18. During the AP Exam
Use the language of statistics in the context of the problem. Give answers that make sense in the context of the problem. For instance, it generally makes no sense to talk about "1/3 of an airplane."
Don’t be sloppy in choice of words. For instance, on a residual graph, the phrase "half are above and half are below" is not equivalent to "randomly scattered.“
Define symbols you introduce.

19. During the AP Exam
Be careful when using "calculator language." It is important for a reader to understand what is written and feel that you really know and understand what you wrote as a response to a problem.
Look at graphs and displays carefully. For graphs, note carefully what is represented on the axes, and be aware of number scale. Some questions that provide tables of numbers and graphs relating to the numbers can be answered simply by "reading" the graphs.

20. During the AP Exam
When AP instructions say "Give appropriate statistical evidence to support your conclusion," or "Justify, using statistical evidence," this means you need to conduct a formal hypothesis testing. This includes:
1. Stating the hypothesis in context of the problem.
2. Naming the test used and why it was used, and checking (not just naming) the conditions or assumptions for the test used. A rough sketch of the "shape" of the data might be helpful here.
3. Carrying out the mechanics of the test and giving a numerical test statistic and a p-value.
4. Writing the conclusion in context. The test statistics must be linked to the conclusion. Example: "Since the p-value is so small (alpha < .05), I reject the null hypothesis and conclude that there is no association between hikers ability and direction traveled when lost."

21. During the AP Exam Don’t mix up the null and alternate hypothesis.
Always check assumptions for significance tests AND confidence interval
When given data, always check assumptions instead of just saying something like "it is assumed....". For instance, in a chi-square test where cell counts are known, if all expected counts are greater than or equal to 5, this should be noted, as contrasted to just stating the assumptions for chi-square.
Interpret p-values correctly and in the context of the problem.

22. After the AP Exam When it is over, you are done.
If you know you prepared to the best of your ability and you tried to do the best job you could on the test, then that is the best anyone can ask of you (even me).
So stop worrying about your score…..(yeah, I know that’s easy for me to say, I didn’t take the test)!
You will know your score before I do – me!