Exam, Calc & Computer Output Tips

Thanks to many colleagues for tips

Dr. DavidsonMallard Creek High School

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For an electronic copy of this presentation, please email me:

Lewis.Davidson@cms.k12.nc.us

Quick questions – call me at home704-786-0470

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9 Years - Questions & Answers

http://www.collegeboard.com/student/testing/ap/statistics/samp.html?stats

Or go to http://www.collegeboard.com • Student• AP• Statistics• Sample Questions & Scoring

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Exam booklet Insert• An insert in the exam booklet contains the

questions without the answer spaces• Remove it from the exam booklet and use

it for reference• No credit is given for anything written on

the insert (the readers do not see it)• Write answers and all your work for each

problem in the pages in the exam booklet!

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Get Familiar with Exam Format• Look at 2011 Exam - (link on previous

slide)• Pages 3 – 5:

Formulas - understand them!• Pages 11 – 14:

Tables - understand them! What do they mean?How do we use them?

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Multiple Choice• Answer every question . (period)• Answer every question . (period)• Answer every question . (period)• Do all work in test book and circle answers

there• Only bubble when you are done – but be

sure you leave time to bubble. • Please DO YOUR BEST to NOT ERASE!.

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Free Response Questions• Must move fast & write only what is needed -

most kids report not enough time• 1st: Five comprehensive questions (75%)

• They usually include different parts of our course• 1st Question: Plan ≤ 10 minutes (often Descriptive)• Next four: average ≈ 12 minutes each

2nd: Investigative Task (25 % of FR Score)• Plan on 25 minutes – Just follow the prompts!

Game Plan• Many say 1st read all questions – Dr. D.

disagrees. -- “Not enough time”, I say• Consider this approach

1. Do Q#1: It is usually the easiest & fastest - 10 Minutes MAXIMUM

2. Work on Q#6 – Investigative task, unless you have no idea what to do. Usually, just follow the prompts EXACTLY 30 Minutes MAXIMUM

3. Consider Q#2 – 5 in order: Do or skip for now4. Say what you know-you may get partial credit

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The Plays – in EXAM Booklet1. Glance at last sentence or a), b), etc

requests – get a sense of problem2. Start reading from the beginning of the

question, but for now just scan long scenario descriptions – now you understand the problem

3. Now read carefully from the start and underline the key facts you need

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Free Response Scoring• 1st Readers check for specific attributes

specified in the rubrics (0 – 4 points total)• Then Readers holistically consider your

demonstrated knowledge & set your score• Unlike Multiple Choice:

• Partial Credit is granted!• There are no penalties for wrong

answers

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Free Response Ideas• Write what you best know on the topic

• Some work can earn Partial Credit• Note: Blank = zero!

• Readers “are on your side” and award points based on work shown

• NO “alternate solutions” give it your best shot! (if 2 solutions, your worst one is scored so cross out worst comments)

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Readers must read & understandBe legible! (Dark pencil or pen)

Answers will be copied Write in good sentences! Show a logical flow! Clearly show your work and answer! Use standard statistical jargon! The answer space provided has plenty of

room for what is expected – use it as a guide!

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Misc

• You can bring two calculators to the exam• Can bring extra batteries _DO IT• Bring at least two sharp # 2 Pencils• Bring a super eraser! -- Note if the

scanner can’t read one of your answers, you will not know it!

Ten Lessons Learned in 10+ Years as an

AP Statistics Exam Reader

Daren StarnesThe Lawrenceville School

dstarnes@lawrenceville.org

BFW Publishers

April 28, 2009

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#10: Read the question--twice!2008 AP Exam, Free Response Question 1To determine the amount of sugar in a typical serving of breakfast cereal, a student randomly selected 60 boxes of different types of cereal from the shelves of a large grocery store. The student noticed that the side panels of some of the cereal boxes showed sugar content based on one-cup servings, while others showed sugar content based on three-quarter-cup servings. Many of the cereal boxes with side panels that showed three-quarter-cup servings were ones that appealed to young children, and the student wondered whether there might be some difference in the sugar content of the cereals that showed different-size servings on their side panels.

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#10: Read the question--twice!

To investigate the question, the data were separated into two groups. One group consisted of 29 cereals that showed one-cup serving sizes; the other group consisted of 31 cereals that showed three-quarter-cup serving sizes.

The boxplots display sugar content (in grams) per serving of the cereals for each of the two serving sizes.

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#10: Read the question--twice!

(a) Write a few sentences to compare the distributions of sugar content per serving for the two serving sizes of cereals.

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#10: Read the question--twice!2008 AP Exam, Free Response Question 1To determine the amount of sugar in a typical serving of breakfast cereal, a student randomly selected 60 boxes of different types of cereal from the shelves of a large grocery store. The student noticed that the side panels of some of the cereal boxes showed sugar content based on one-cup servings, while others showed sugar content based on three-quarter-cup servings. Many of the cereal boxes with side panels that showed three-quarter-cup servings were ones that appealed to young children, and the student wondered whether there might be some difference in the sugar content of the cereals that showed different-size servings on their side panels.

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#10: Read the question--twice!

To investigate the question, the data were separated into two groups. One group consisted of 29 cereals that showed one-cup serving sizes; the other group consisted of 31 cereals that showed three-quarter-cup serving sizes.

The boxplots display sugar content (in grams) per serving of the cereals for each of the two serving sizes.

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#9: Answer the question!(a) Write a few sentences to compare the distributions of sugar content per serving for the two serving sizes of cereals.

Shape 1-cup: Left skewed¾-cup: Roughly symmetric

Center More sugar for 1-cup cereals than ¾-cup cereals (medians are 13g & 10g)

Spread More variability for 1-cup cereals than ¾-cup cereals (IQRs are 11g & 4 g)

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#8: Don’t shoot yourself in the foot!

• Shape– Skewed which way?– “Normal”?!

• Center– Mean?!

• Spread– Standard deviation?!

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#7: Avoid calculator speak

(1) Binompdf(12,.2,3) = no full credit• Better: P(X = 3) = (12C3)(0.2)3(0.8)9

• OK: binompdf with n = 12, p = .2, k = 3

(2) Normalcdf(90,105,100,5) = no full credit• Better: draw, label, shade Normal curve• OK: normalcdf with low bound = 90, high

bound = 1-5, mean = 100, std. dev. = 5

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#6: Naked answer = no credit

• Directions: Show all your work. Indicate clearly the methods you use, because you will be graded on the correctness of your methods as well as on the accuracy and completeness of your results and explanations.

From 2008 Exam, FR Question 3• “Calculate the expected score for each player.”• “Find the probability that the difference in their

scores is -1.”

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#5: Know your inference methods

2008 AP Exam, Free Response Question 5A study was conducted to determine where moose are found in a region containing a large burned area. A map of the study area was partitioned into the following four habitat types.(1) Inside the burned area, not near the edge of the burned area,(2) Inside the burned area, near the edge,(3) Outside the burned area, near the edge, and(4) Outside the burned area, not near the edge.

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The study areaThe figure below shows these four habitat types.

The proportion of total acreage in each of the habitat types was determined for the study area.

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Aerial survey resultsUsing an aerial survey, moose locations were observed and classified into one of the four habitat types. The results are given in the table below.

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#5: Know your inference methods

(a) The researchers who are conducting the study expect the number of moose observed in a habitat type to be proportional to the amount of acreage of that type of habitat. Are the data consistent with this expectation?Conduct an appropriate statistical test to support your conclusion. Assume the conditions for inference are met.

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#5: Know your inference methods

• What percent of students at your school have a MySpace page?

• Is there a relationship between students’ favorite academic subject and preferred type of music at a large high school?

• VERY-VERY Helpful web site: http://www.ltcconline.net/greenl/java/Statistics/StatsMatch/StatsMatch.htm

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#4: Don’t skip the investigative task

Part BQuestion 6Spend about 25 minutes on this part of the exam.Percent of Section II score—25

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#3: Beware mandatory deductions

• Saying “experiment” for an observational study

• “Confounding” when there isn’t• Using incorrect symbols: eg statistics in a

hypothesis

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#2: Only use terms and symbols you know

• It’s better to explain in your own words than to use a technical term incorrectly

• If you’re unsure about notation, use words instead of symbols

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#1: Don’t write too much

• Answer the question asked and only, the qustioned asked; then STOP !

• Space provided is more than enough• Remember the mandatory deduction rule

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Ten Lessons Learned: Recap#10: Read the question--twice!#9: Answer the question!#8: Don’t shoot yourself in the foot!#7: Avoid calculator speak#6: Naked answer = no credit#5: Know your inference methods#4: Don’t skip the investigative task#3: Beware mandatory deductions#2: Only use terms and symbols you know#1: Don’t write too much

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1. Don’t change an answer unless you have a reason of which you are very sure

2. State all assumptions & check conditions3. Answer all parts of the Free Response

questions – Make up an answer you don’t know if needed for the next part

4. Label and scale all graphs

Mrs. Lerner’s Top AP Exam Tips

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5. Don’t give ‘parallel’ solutions on the Free Response questions

6. Write neatly7. Write all conclusions in context8. Read all the words (just skimming “long

scenario statements”) and understand what the question is asking (usually it is at the end)

Mrs. Lerner’s Top AP Exam Tips