Written Response 2: Algorithms, errors and testing, and abstraction

Free-throw simulation

Unit 3
3 points
About 45 minutes

Three prompts about the program's code. (a) Algorithm development: explain how a loop or condition works, such as how many times a loop runs or what makes it stop. (b) Errors and testing: describe a call, input or change that causes an error or wrong behavior and explain why. (c) Data and procedural abstraction: explain how the list or procedure manages complexity, or explain, step by step, an algorithm that uses the list. On the exam: Question 2 of 2 (3 points: parts (a), (b) and (c) are worth 1 point each). Section II has 2 written-response questions (4 prompts) in 60 minutes, taken in Bluebook at the end-of-course exam; no calculator. On the real exam the questions are about your own Create performance task program, and you can see your Personalized Project Reference (screenshots of your procedure and list code). The Create task is 30% of the AP score, scored on 6 one-point rows: video, program requirements, WR1, WR2(a), WR2(b) and WR2(c). On this site you answer the same kinds of prompts about a short sample program given with the question.

The question and its sources

Answer parts (a), (b) and (c) about the sample program below. On the exam these prompts are about your own Create task program and your Personalized Project Reference; here, the code segments below play that role. Refer to the specific code in every answer, and write in complete sentences.

About the program

A coach uses a simulation to estimate how many free throws, out of 20, players with different shooting percentages might make. simulateShots(numShots, percentMade) is meant to model a player who makes each shot with a percentMade percent chance. The list percentages holds four players' shooting percentages.

Each run displays each percentage followed by that player's simulated number of makes. Because the simulation uses RANDOM, the numbers vary from run to run.

Source: Sample program written for this practice question (hypothetical)

Procedure: simulateShots

Pseudocode

PROCEDURE simulateShots(numShots, percentMade)
{
    made ← 0
    REPEAT numShots TIMES
    {
        IF(RANDOM(1, 100) < percentMade)
        {
            made ← made + 1
        }
    }
    RETURN(made)
}

Source: Sample program written for this practice question (hypothetical)

List: storing the percentages in percentages

Pseudocode

percentages ← [72, 85, 100, 60]

Source: Sample program written for this practice question (hypothetical)

Calling the procedure and using the list

Pseudocode

FOR EACH p IN percentages
{
    DISPLAY(p)
    DISPLAY(simulateShots(20, p))
}

Source: Sample program written for this practice question (hypothetical)

Suggested time: 45 minutes

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Part (a)

1 point

Identify the number of times the body of the iteration statement in simulateShots executes during one call made by this program, and the total number of times it executes during one full run of the program. Explain how you know.

Your answer to part (a)

0 / 2,500 characters

Part (b)

1 point

Write a call to simulateShots with specific argument(s) that the procedure accepts but that cause it to behave incorrectly. Describe the incorrect behavior, and explain why it happens as a result of your call. If no call with accepted arguments can make simulateShots behave incorrectly, explain why.

Your answer to part (b)

0 / 2,500 characters

Part (c)

1 point

Explain how the list percentages uses abstraction to manage complexity in this program. Then suppose the program did not use a list. Describe how the code that uses the list would have to change to keep the same behavior, or explain why the same behavior would not be possible without a list.

Your answer to part (c)

0 / 2,500 characters

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