Transcript Tips for Writing Free Response Questions on the AP Statistics Exam

General Set up of the exam
Two Sections
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Multiple Choice
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90 minutes
40 questions
Free Response
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90 minutes
6 questions (5 shorter, 1 longer)
Topics
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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
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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
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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 onevariable distributions. You’ll need to compare
center, shape and spread.
Common Task: Test of Significance
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Hypothesis Test rubrics generally look for four
components:
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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
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Be clear, brief, and explicit.
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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

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Never contradict yourself.
NEVER write calculator commands.
Never? Never. Never ever. Not even once.
Period.
 Remember binomial distribution?
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Writing Tips
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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!!!
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Writing Tips
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Do not use pronouns!
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“It is higher.” WHAT is higher?
Don’t use no double negatives.
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I fail to reject that I don’t believe that the
data are not independent.
Common Student Errors
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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.
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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.
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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.
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Common Student Errors
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You need to know the difference between
taking a simple random sample and
randomly allocating subjects to treatment
groups.
Common Topics
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Exploratory Data Analysis
 One-variable
 Descriptive
data
statistics: Center, Shape, Spread
 Two-variable
data
 Correlation,
regression, residual plots, coefficient
of determination
Hypothesis Tests
 Probability
 Experimental Design
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In the end…
It’s not what you know.
 It’s what you can SHOW that you know.
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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)
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Calculator
You can use your own (no higher than Ti89)
 Take extra batteries
 I will send extras.
 Make sure you have Diagnostic On… Let’s
do this now.
 Your calculator will not be cleared.
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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
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Do not schedule work for before 4:00
 Do your best!
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Materials for Review
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http://apcentral.collegeboard.com/apc/me
mbers/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/me
mbers/exam/exam_information/8357.html
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