Data
Represent and investigate data
Use binary, compression, metadata, and data cleaning without losing the meaning of a dataset.
Algorithm examples use AP reference notation, including one-based list indices.
Bits represent a choice
One bit has two possible values. Eight bits can represent 256 different patterns. The pattern 01000001 means 65 as an unsigned integer, but can mean a letter under a character encoding. The bits do not carry their interpretation with them.
Lossless compression permits exact reconstruction, which matters for program files. Lossy compression removes information to save space, which may be acceptable for a photo. A smaller file is not automatically a more accurate file.
Ask what the dataset omits
Before averaging journey times, check whether times are recorded in seconds or minutes, remove impossible entries, and decide how to treat missing values. Metadata describes details such as units, collection date, and the meaning of a column.
A pattern in a dataset can suggest a question, but correlation alone does not establish a cause. If only students with smartphones supplied journey data, the results may not describe every student at the school.
Check yourself
Would lossy compression be appropriate for a file of program instructions?Show answer
No. Removing or changing even one instruction could change the program. Use lossless compression when exact recovery matters.
References used to build these lessons
We used these official documents as references when building this course's lessons. They are the sources for the syllabus structure and course requirements.
College Board · Effective fall 2023