Two Sections • Multiple Choice • 90 minutes • 40 questions • Free Response • 90 minutes • 6 questions (5 shorter, 1 longer) • Topics • Exploring data (describing patterns and departures from patterns) • Sampling and experimentation (planning and conducting a study) • Anticipating patterns (producing models using probability and simulation) • Statistical inference (estimating population proportions and testing hypotheses).
Multiple Choice • 1 point for a correct answer • 0 for no answer • Counts 50% of your grade
Free Response • 50% of your grade • Questions 1-5 are 15% each of free response grade • Question 6 is 25% of free response grade • Score is a 0-4
Tips for Writing Free Response Questions on the AP Statistics Exam
It should be obvious… • Read the question. Answer the question. No more, no less.
Common Task: Choose • If you are asked to choose between two things (fuel additive A or fuel additive B), state why you would choose one AS WELL AS why you would NOT choose the other. However , be careful not to contradict yourself!
Common Task: Compare • If you are asked to compare, make less than/greater than statements. • Compare like things. Never compare a median of one distribution to the 1st quartile of another. Instead, compare the median of distribution A to the median of distribution B. • AP Questions often ask you to compare one-variable distributions. You’ll need to compare center, shape and spread.
Common Task: Test of Significance • Hypothesis Test rubrics generally look for four components: • State the hypotheses with the correct symbols. Define any subscripts. • Identify (by NAME or by FORMULA) a test-statistic. State and check the assumptions. • Calculate the value of the test-statistic. Calculate the p-value and compare it to alpha. Reject or fail to reject the null hypothesis. • State your conclusion in words in the context of the problem.
Writing Tips • Be clear, brief, and explicit. • If you ramble on and on, you’re likely to contradict yourself. Plus, when a student is brief, it is clear that he/she knows what the question is asking and how to answer it.
Writing Tips • Never contradict yourself. • NEVER write calculator commands. • Never? Never. Never ever. Not even once. Period. • Remember binomial distribution?
Writing Tips • Be careful about strong language. • One sample design question asked why we randomly allocate subjects to treatment groups. If students stated that random allocation ELIMINATES bias, they were given NO credit. • You never PROVE anything!!!
Writing Tips • Do not use pronouns! • “It is higher.” WHAT is higher? • Don’t use no double negatives. • I fail to reject that I don’t believe that the data are not independent.
Common Student Errors • Realizing that when the directions say “Give appropriate statistical evidence to support your conclusion” or “Justify, using statistical evidence” students are asked to conduct FORMAL hypothesis tests. • Realizing that when you write the words “on average” that you’re referencing the mean. • Using non-statistical words to convey a statistical concept. • The graph is “even.” ??? Do they mean uniform? Symmetric? Normal? • The residual plot is “half above and half below.” I think they meant uniformly scattered.
Common Student Errors • The amount of space left for students to answer the question is NOT an indication of how much you should write. • Expected value = mean. • When stating assumptions, saying the data are normal or the distribution is normal is not correct. • The correct assumption is that the population is distributed normally. We check that assumption by looking at the distribution of the sample data.
Common Student Errors • Students tend to confuse skewed right and skewed left. • Students tend to confuse symmetric with approximately normal. • Students tend to list everything they know and hope that part of it is correct. This is called a “parallel solution.” The graders will grade the weakest of the solutions.
Common Student Errors • You need to know the difference between taking a simple random sample and randomly allocating subjects to treatment groups.
Common Topics • Exploratory Data Analysis • One-variable data • Descriptive statistics: Center, Shape, Spread • Two-variable data • Correlation, regression, residual plots, coefficient of determination • Hypothesis Tests • Probability • Experimental Design
In the end… • It’s not what you know. • It’s what you can SHOW that you know.
Some college credit • UNC Chapel Hill… 3 or more • NC State… 3 or more • UNCC… 3 or more • Appalachian… 3 (one class), 4 or 5 (two classes)
Calculator • You can use your own (no higher than Ti-89) • Take extra batteries • I will send extras. • Make sure you have Diagnostic On… Let’s do this now. • Your calculator will not be cleared.
On the day of the test • Take pencils!!!! • Take your calculator • Get some rest the night before • Get to your testing site at 11:30 • Do not schedule work for before 4:00 • Do your best!
Materials for Review • http://apcentral.collegeboard.com/apc/members/exam/exam_tips/4073.html#name4 • Click on AP Statistics Exam Tips for Students • Borrow an AP Review Book • Check out the links on my website • http://apcentral.collegeboard.com/apc/members/exam/exam_information/8357.html