College Board Unit 4
How it works
Data and its implications is the reasoning topic added to the 2026 AP CSA framework. It asks what a program should collect, what its data can and cannot express, and who is affected by the answers. The technical side is familiar: how a data type limits what can be represented, how integer division silently discards a remainder in an average, and how one outlier moves a mean but not a median. The reasoning side asks who is missing from the data, what a summary hides, and whether an individual could be identified from what was stored.
For any program handling personal data, state what is collected, why it is needed, and who can see it.
Common error
Treating data questions as opinion. They expect reasoning about specific, identifiable consequences.
Worked example
A tutoring center wants to identify topics that need review. Collecting anonymous topic-level error counts answers that question without publishing named student scores. Limit access to identifiable records and define a deletion schedule.
Exercises
8.6.1 · Explain
A school surveys only robotics-club members to decide which programming class all students want. Identify a sampling problem and propose a better collection method.
Show solution
Robotics-club members are likely to have more programming interest and experience than the full student population. Survey a representative sample across grades and experience levels, or invite the full student body and evaluate nonresponse.
8.6.2 · Design
A practice app stores student names, birth dates, full location histories, and topic scores forever. It needs only to recommend review topics. Propose three concrete changes and explain their benefits.
Show solution
Keep only information needed for recommendations, such as a student identifier and recent topic scores. Remove birth dates and location histories unless a separate necessary purpose justifies them. Restrict access and use a short retention/deletion policy. These changes reduce exposure while preserving the recommendation function.