Big Idea 2 Unit Test: Data | AP CSP Practice Test

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Big Idea 2 • Data

Big Idea 2 Unit Test: Data

📝 12 questions 🎯 AP exam difficulty ✅ Auto-scored

📋 Unit Test instructions

This unit test covers all of Big Idea 2: binary numbers, data compression, extracting information from data, and using programs with data.

Answer all 12 questions, then press Submit test. You will see your score, which questions you missed, and the correct answer with an explanation. Passing is 70%, the AP benchmark. You can retake it.

0 of 12 answered

Question 1 of 122.1 Binary Numbers

A single bit stores one binary digit, and 8 bits form one byte. A program uses exactly 8 bits to store an unsigned whole number. Which statement about what those 8 bits can represent is correct?

Answer: A. Correct. With n bits there are 2^n combinations, so 8 bits give 2^8 = 256 values, and starting at 0 the range is 0 to 255.

Question 2 of 122.1 Binary Numbers

Convert the unsigned binary number 1011 0010 to decimal. What is its value?

Place values: 128  64  32  16   8   4   2   1
Bits:           1    0   1   1   0   0   1   0

Answer: A. Correct. The set bits are 128 + 32 + 16 + 2 = 178.

Question 3 of 122.1 Binary Numbers

A digital thermometer measures temperature, which changes smoothly and continuously, and stores each reading using a fixed number of bits. Which pairing of ideas is described here?

I. The real temperature is analog data because it varies continuously.
II. Storing the reading in a fixed number of bits makes it digital, so some precision may be lost as roundoff.
III. A fixed number of bits guarantees the stored reading is exactly equal to the real temperature.

Answer: D. Correct. Continuous temperature is analog; representing it with a fixed number of bits digitizes it and can introduce roundoff, so I and II hold while III does not.

Question 4 of 122.2 Data Compression

A team must email a legal contract as a text file and later reconstruct every character exactly. Which compression choice fits, and why?

Answer: C. Correct. Lossless compression reduces size while allowing the exact original to be reconstructed, which the contract requires.

Question 5 of 122.2 Data Compression

Run-length encoding replaces long runs of repeated symbols with a symbol and a count. For which input would run-length encoding produce the SMALLEST compressed size relative to the original?

Option W: AAAAAAAAAAAAAAAA   (16 identical symbols)
Option X: ABABABABABABABAB   (alternating symbols)
Option Y: ABCDEFGHIJKLMNOP   (all different)
Option Z: AABBCCDDEEFFGGHH   (pairs)

Answer: D. Correct. Run-length encoding exploits redundancy, and 16 identical symbols form one long run that compresses to a single symbol and count.

Question 6 of 122.2 Data Compression

A student claims, "A smaller file always carries less information than a larger file." Why is this claim FALSE according to the framework?

Answer: B. Correct. Lossless compression shrinks a file by removing redundancy while preserving all information, so fewer bits does not have to mean less information.

Question 7 of 122.3 Extracting Information

An analyst has a spreadsheet of one million online orders and wants to study only orders placed in December that were over 50 dollars. Which process most directly produces that focused subset?

Answer: C. Correct. Filtering selects only the records that satisfy stated conditions, producing the December, over-50-dollar subset.

Question 8 of 122.3 Extracting Information

A city reports that in months when ice cream sales are high, the number of pool-drowning incidents is also high, so the two rise and fall together. Which conclusion is best supported?

Answer: C. Correct. The data show correlation, but correlation does not imply causation, and a hidden factor such as warm weather likely raises both.

Question 9 of 122.3 Extracting Information

A photo file stores the image itself plus the date taken, camera model, and GPS location. The date, camera model, and GPS location are best described as which of the following?

Answer: A. Correct. Data that describes other data, such as when and where a photo was taken, is metadata.

Question 10 of 122.4 Using Programs with Data

Before analysis, a program processes survey responses that include duplicate submissions, blank entries, and states written as both "CA" and "California." Which step is this, and what is its main goal?

Answer: B. Correct. Cleaning removes duplicates and blanks and standardizes inconsistent formats so later analysis is trustworthy.

Question 11 of 122.4 Using Programs with Data

The pseudocode below builds a cleaned list from raw sensor readings. Which statement best describes what it accomplishes?

cleaned <- []
FOR EACH reading IN rawData
{
  IF (reading >= 0)
  {
    APPEND(cleaned, reading)
  }
}
DISPLAY(LENGTH(cleaned))

Answer: D. Correct. The loop filters out negative (invalid) readings, appends the valid ones to cleaned, and displays the count kept.

Question 12 of 122.4 Using Programs with Data

An analyst tests a data-processing program on 500 rows, and it runs quickly and correctly. The real data set will contain 500 million rows. Which concern is most important to evaluate next?

Answer: B. Correct. A method that works on a small sample may be far too slow or memory-heavy at scale, so scalability is the key concern.

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