AP STATISTICS: The Test REASON/THINK and COMMUNICATE

Info on Multiple Choice The AP Stat Exam has of two sections: Section I 40 Multiple-Choice questions 90 minutes Counts 50 percent of exam score SCORING: 1 point for each correct answer 0 points for each question left blank or for each incorrect answer

Info free response Section II Free-Response questions 90 minutes counts 50 percent of exam score Questions are designed to test your statistical reasoning and your communication skills. SCORING: Five open-ended 13 minutes; each counts 15 percent of free-response score (5x15%=75% of free response score) One investigative 25 minutes; counts 25% percent of free-response score

Scoring on free response Each free-response question is scored on a 0 to 4 scale. General descriptors for each of the scores are: 4= Complete Response -NO statistical errors and clear communication 3= Substantial Response - Minor statistical error/omission or fuzzy communication 2= Developing Response - Important statistical error/omission or lousy communication 1= Minimal Response - A "glimmer" of statistical knowledge related to the problem 0= Inadequate Response - No glimmer; statistically dangerous to himself and others

AP graders are most interested in your reasoning and communication!

During the Exam General Advice 1. Relax, and take time to think! Remember that everyone else taking the exam is in a situation identical to yours. Realize that the problems will probably look considerably more complicated than those you have encountered in other math courses. That's because a statistics course is, necessarily, a "wordy" course.

General Advice #2 2. Manage your time. Take a few minutes to skim #1-5 and suss out and note the type of problem: gof, bin, HT 2 p’s, center/shape/spread,…etc. This will help you start with the material you know best and let your brain marinate on some of the others.

General Advice #3 3. Read each question carefully before you begin working. This is especially important for problems with multiple parts or lengthy introductions. Suggestion: READ ACTIVELY..Underline key words and phrases as you read the questions. Often there are clues/hints in other parts of the problem that can help you get started.

General Advice #4 4 COMPARE! This word means that the scorers need to see you explicitly draw comparisons …for example you are comparing graphs/data on performance on a relay race between staff and students…you would want to address center(staff and students, then shape (staff and students) and spread (staff students)…format wisely and include context/units!!

General Advice #5 5. Take the “goldilocks” approach to answering the questions….not too much detail (don’t go off on a tangent, start to rant on a related topic or try and write everything you know on 1a)….but no too little (don’t forget units/context…be sure to answer exactly what they ask.

General Advice #6 6. 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. Don’t forget to analyze in context

General Advice #7 About graphing calculator use: Your graphing calculator is meant to be a tool, to be used sparingly on some exam questions. Your brain is meant to be your primary tool. Don’t use “TI talk” in your exam

On multiple-choice questions: Examine the question carefully. What statistical topic is being tested? What is the purpose of the question? Read carefully. Underline key words and phrases. After deciding on an answer, glance at the highlighted words and phrases to make sure you haven't made a careless mistake or an incorrect assumption. Careless mistakes hurt. If you can eliminate more than one answer choice, you might benefit by guessing. You don't have to answer all of the questions to get a good overall score. If an answer choice seems "obvious," think about it. If it's so obvious to you, it's probably obvious to others, and chances are good that it is not the correct response. Don’t waste time/stress out trying to “out think” the scoring*

On free-response questions: You don't have to answer a free-response question in paragraph form. Sometimes an organized set of bullet points or an algebraic process is preferable. [clearly id test by formula or name] Answer each question in context. Read each question carefully, sentence by sentence, and underline key words or phrases.

On free-response questions: Do not feel pressured to work the free-response problems in a linear fashion, for example, 1, 2, 3, 4, 5, 6. Read all of the problems before you begin. Question 1 is meant to be straightforward, so you may want to start with it. Then move to another problem that you feel confident about. Whatever you do, don't run out of time before you get to Question 6 - the Investigative Task. –[know your “testing style”] Decide what statistical concept/idea is being tested. This will help you choose a proper approach to solving the problem.

#6 Investigative task These questions often –Include material from several different chapters- carefully read all parts of the problem looking for key words or phrases – HINTS! –May define new formulas or terminology – go with it –Are trying to determine the depth of your understanding of statistics (and your confidence in that knowledge)…have some faith in yourself and “go for it”

Free Response Questions - recap Don’t run out of time for #6. This investigative task counts almost twice as much as the other questions (#1-5 15% ea, #6 25%) Decide what statistical concept/idea is being tested-diagnose the problem. This will help you choose a proper approach to solving the problem Answer each question in context: Conditions, formula or name of test, summary sentences

Free Response tips The space provided on the test doesn’t necessarily indicate the amount you should write If you cannot get an answer to a part of “a” question, make up a plausible answer to use in the remaining parts of the problem (especially useful in Calculus)

Write efficiently. Say what needs to be said and move on Don’t contradict yourself Look back at your answer – does it make sense? Did you address the question asked? Don’t write “everything you know” (you’ll be graded on it) stick to the problem

GRAPHS: Label and scale axes Don’t refer to a graph on your calculator you haven’t drawn Analyze the results! Don’t just draw it. If given a graph, Carefully note axes and scale

You’ve got this!!! I know you do

Exploring data: Analyzing one-variable data Shape, center, and spread Look for patterns, then deviations from patterns Don’t confuse median and mean Don’t confuse standard deviation and variance Transformations of data sets Add/sub “k” to each element of data changes mean and median by k, doesn’t change st. dev or IQR Mult by “k” mean, median, IQR and st dev mult by k (var by k^2)

Surveys, Observational Studies and Experiments SRS refers to how you obtain sample, random allocation is what you use in an experiment to assign subjects to treatment groups (not the same!) Control for effects of lurking variables in an experiment design Randomization: allocation to treatment groups – should help avoid bias and lurking variables Replication – large enough n (or repeated experiments) Blocking: grouping of subjects in an experiment to avoid unwanted variability

Probability Independence is not the same as mutually exclusive events Recognize a discrete random variable setting (text ch 18) – be able to calculate mean (or expected value) and standard deviation Recognize binomial situations and when it can be approximated by normal curve

Simulations Create a correspondence between random numbers and outcomes (ex. odd # = made basket, even # = miss) Explain how you will obtain random numbers (table, GC, etc) Describe purpose of simulation and how you will calculate an answer – if the question calls for that Are you drawing numbers with or w/o replacement…describe special cases and how your simulation will work

Hypothesis Tests State Ho and Ha in terms of the population parameters (not sample stat.)…except for some chi-square’s use symbols not words Don’t reverse null and alternate hypothesis (null hyp should be a statement of no effect or difference and have “=“) Don’t confuse paired samples with two populations means (know which calc buttons are which !) Type I error: reject Ho when true Type II: Accept Ho when false Power of a test = probability of correctly rejected a null hypotheses [1 – P(type II error)]

RELAX!! You’ve done the hard part (the class, the studying, etc.). Try to relax and just do the best job you can.