General Set up of the exam

Two Sections Multiple Choice Multiple Choice 90 minutes 90 minutes 40 questions 40 questions Free Response Free Response 90 minutes 90 minutes 6 questions (5 shorter, 1 longer) 6 questions (5 shorter, 1 longer) Topics Topics Exploring data (describing patterns and departures from patterns) Exploring data (describing patterns and departures from patterns) Sampling and experimentation (planning and conducting a study) Sampling and experimentation (planning and conducting a study) Anticipating patterns (producing models using probability and simulation) Anticipating patterns (producing models using probability and simulation) Statistical inference (estimating population proportions and testing hypotheses). Statistical inference (estimating population proportions and testing hypotheses).

Multiple Choice 1 point for a correct answer 1 point for a correct answer 0 for no answer 0 for no answer Counts 50% of your grade Counts 50% of your grade

Free Response 50% of your grade 50% of your grade Questions 1-5 are 15% each of free response grade Questions 1-5 are 15% each of free response grade Question 6 is 25% of free response grade Question 6 is 25% of free response grade Score is a 0-4 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. 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. 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. 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. 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. 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: Hypothesis Test rubrics generally look for four components: State the hypotheses with the correct symbols. Define any subscripts. State the hypotheses with the correct symbols. Define any subscripts. Identify (by NAME or by FORMULA) a test-statistic. State and check the assumptions. 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. 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. State your conclusion in words in the context of the problem.

Writing Tips Be clear, brief, and explicit. 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. 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 contradict yourself. NEVER write calculator commands. NEVER write calculator commands. Never? Never. Never ever. Not even once. Period. Never? Never. Never ever. Not even once. Period. Remember binomial distribution? Remember binomial distribution?

Writing Tips Be careful about strong language. 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. 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!!! You never PROVE anything!!!

Writing Tips Do not use pronouns! Do not use pronouns! “It is higher.” WHAT is higher? “It is higher.” WHAT is higher? Don’t use no double negatives. Don’t use no double negatives. I fail to reject that I don’t believe that the data are not independent. 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 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. Realizing that when you write the words “on average” that you’re referencing the mean. Using non-statistical words to convey a statistical concept. Using non-statistical words to convey a statistical concept. The graph is “even.” ??? Do they mean uniform? Symmetric? Normal? 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. 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. The amount of space left for students to answer the question is NOT an indication of how much you should write. Expected value = mean. Expected value = mean. When stating assumptions, saying the data are normal or the distribution is normal is not correct. 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. 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 skewed right and skewed left. Students tend to confuse symmetric with approximately normal. 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. 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. You need to know the difference between taking a simple random sample and randomly allocating subjects to treatment groups.

Common Topics Exploratory Data Analysis Exploratory Data Analysis One-variable data One-variable data Descriptive statistics: Center, Shape, Spread Descriptive statistics: Center, Shape, Spread Two-variable data Two-variable data Correlation, regression, residual plots, coefficient of determination Correlation, regression, residual plots, coefficient of determination Hypothesis Tests Hypothesis Tests Probability Probability Experimental Design Experimental Design

In the end… It’s not what you know. It’s not what you know. It’s what you can SHOW that you know. It’s what you can SHOW that you know.

Some college credit UNC Chapel Hill… 3 or more UNC Chapel Hill… 3 or more NC State… 3 or more NC State… 3 or more UNCC… 3 or more UNCC… 3 or more Appalachian… 3 (one class), 4 or 5 (two classes) Appalachian… 3 (one class), 4 or 5 (two classes)

Calculator You can use your own (no higher than Ti- 89) You can use your own (no higher than Ti- 89) Take extra batteries Take extra batteries I will send extras. I will send extras. Make sure you have Diagnostic On… Let’s do this now. Make sure you have Diagnostic On… Let’s do this now. Your calculator will not be cleared. Your calculator will not be cleared.

On the day of the test Take pencils!!!! Take pencils!!!! Take your calculator Take your calculator Get some rest the night before Get some rest the night before Get to your testing site at 11:30 Get to your testing site at 11:30 Do not schedule work for before 4:00 Do not schedule work for before 4:00 Do your best! Do your best!

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