Lesson 4
Summation notation
Big question
How do we write 'add all these values' in one symbol?
Lesson progress
Complete checkpoints as you learn
Learning objectives
- Explain summation notation in plain language.
- Use summation correctly in an interpretation.
- Connect the lesson idea to a formula, graph, Python result, or real example.
Simple explanation
The summation symbol tells us to add a list of values. In econometrics, it appears in averages, variance, covariance, and many formulas that summarize all observations in a dataset.
Key terms
- Summation
- A compact instruction to add values across observations.
- Index
- The counter that tells us which value to use each time.
- Sample size
- The number of observations in the dataset, often written as n.
- Total
- The result after adding values together.
Add all wages
Example
For wages 18, 22, and 30, the summation is 18 + 22 + 30 = 70.
Sum values in Python
1wages = [18, 22, 30]2total_wages = sum(wages)3print(total_wages)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 the sigma symbol ask us to do?
Key takeaway
Summation notation is just a short way to say add values over many observations.