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AP Computer Science Principles Unit 2: Data

12 questions

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Unit 2: Data

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Question 1

A survey of 10,000 adults asks: "Do you use social media daily?" Results show 68% say yes. A researcher concludes that 68% of all humans use social media daily.

Which flaw in this data analysis is MOST significant?

A.The sample size is too small — surveys need at least 1 million respondents to draw valid conclusions.B.The survey uses lossy compression, which distorted the responses.C.The conclusion overgeneralizes from a non-representative sample — adults surveyed in one context may not represent all humans (including children and people without internet access).D.The binary yes/no encoding of responses is insufficient and introduces rounding errors.

Question 2

What is the decimal value of the 8-bit binary number 00001011?

A.8B.11C.13D.3

Question 3

A data analyst trains a machine learning model to predict loan approval using historical loan data. She later discovers that the historical data reflects past discriminatory lending practices that denied loans to certain demographic groups at higher rates. The model learns from this pattern and replicates it.

This scenario BEST illustrates which concern about data?

A.Data compression — the training data was compressed, removing important information.B.Metadata corruption — the timestamps on the records were inaccurate.C.Bias in data — the training data reflects historical discrimination, causing the model to perpetuate it.D.Lossy encoding — some loan applications were discarded during digitization.

Question 4

Which of the following is an example of data abstraction?

A.Storing a student's grade as the number 92 rather than tracking every individual assignment score that contributed to it.B.Compressing an image file so it takes up less disk space.C.Converting a decimal number to binary so a computer can store it.D.Encrypting a file so unauthorized users cannot read it.

Question 5

ASCII uses 7 bits to encode each character, allowing it to represent 2^7 = 128 characters. Unicode (UTF-32) uses 32 bits per character. Why was Unicode developed?

A.To compress text files so they take up less storage space.B.To represent the characters of virtually all human writing systems, including scripts not covered by ASCII.C.To make programs run faster by replacing multi-byte sequences with single bytes.D.To eliminate the need for binary representation in modern computers.

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Question 6

How many different values can be represented using 3 bits?

A.3B.6C.8D.16

Question 7

A hospital stores patient records in a database. Each record includes the patient's name, date of birth, diagnosis codes, and the date each entry was created. The dates and times when entries were created are examples of which type of data?

A.Primary data — the most important data in the record.B.Compressed data — the dates are stored more efficiently than the diagnosis codes.C.Metadata — data that describes other data, in this case when the records were created.D.Encrypted data — the dates are hidden to protect patient privacy.

Question 8

A photograph is stored in JPEG format (lossy compression) and then decompressed. Which of the following accurately describes the decompressed image?

A.The decompressed image is identical to the original photograph because decompression always restores all data.B.The decompressed image has the same file size as the original uncompressed photograph.C.The decompressed image approximates the original but may differ in subtle ways because some information was permanently discarded.D.The decompressed image is completely unrecognizable because lossy compression destroys most of the image data.

Question 9

A health app automatically logs a user's GPS location every 5 minutes throughout the day. Over a year, this produces a detailed record of everywhere the user went.

Which of the following BEST describes a privacy concern raised by this data collection practice?

A.The GPS data uses too many bits per coordinate, wasting storage space.B.Aggregating location data over time creates a detailed behavioral profile that can reveal sensitive information (home/work address, medical visits, religious attendance) even if each data point seems harmless.C.GPS coordinates are stored as floating-point numbers, which introduces rounding errors that distort the user's location.D.The app should use lossless compression on the location data to prevent privacy breaches.

Question 10

Which of the following BEST distinguishes lossy compression from lossless compression?

A.Lossy compression always produces a smaller file than lossless compression for any type of data.B.Lossless compression allows the original data to be perfectly reconstructed; lossy compression discards some information permanently and cannot perfectly reconstruct the original.C.Lossy compression is used only for text files; lossless compression is used only for images.D.Both lossy and lossless compression permanently remove data to reduce file size.

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Question 11

A digital audio file encodes sound by sampling the audio signal at regular intervals (e.g., 44,100 times per second) and storing each sample as a binary number. Which of the following changes would INCREASE the accuracy of the digital audio representation?

A.Reducing the sampling rate from 44,100 Hz to 22,050 Hz.B.Using fewer bits per sample (e.g., from 16 bits to 8 bits).C.Increasing the sampling rate (e.g., from 44,100 Hz to 96,000 Hz) and using more bits per sample.D.Applying lossy compression to the sampled audio data.

Question 12

A run-length encoding (RLE) scheme compresses a row of pixels by replacing consecutive identical values with a count and the value. For example, the row WWWWBBWW is encoded as 4W2B2W.

Using this scheme, what is the compressed encoding of RRRRRRGGGG?

A.6R4GB.4R6GC.RRRRRRGGGGD.10RG

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