Lesson 7
Time-series data
Big question
What can we learn by tracking one variable through time?
Lesson progress
Complete checkpoints as you learn
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Big question
Concept
Activity
Quiz
Learning objectives
- Explain time-series data in plain language.
- Use time period correctly in an interpretation.
- Connect the lesson idea to a formula, graph, Python result, or real example.
Simple explanation
Time-series data follows a variable over multiple periods. It is useful for studying trends, cycles, growth, inflation, unemployment, interest rates, and GDP.
Key terms
- Time period
- A year, quarter, month, week, day, or other time unit.
- Trend
- A long-run movement over time.
- Seasonality
- A pattern that repeats at regular times.
- Lag
- A past value of a variable.
Time index
Example
Monthly unemployment rates from January 2010 to December 2025 form a time series.
Checkpoint activity
Pause and explain this lesson's main idea in your own words before moving forward.
Try it yourself
Write one plain-English sentence explaining the main idea from this lesson.
Common mistakes
Check these before you move on.
A regression coefficient describes a pattern unless the assumptions or research design support a causal interpretation.
Quick quiz
What does t usually represent in time-series notation?
Key takeaway
Time-series data helps us study economic movement and timing.