Module 7 Worksheet: Sampling Variation and Confidence Intervals
Scenario
A single figure from a sample is about to be quoted in a document that will not carry the interval.
Data
Dataset: confidence-interval-examples.csv
| estimate_id | metric | estimate | lower_ci | upper_ci | sample_size |
|---|---|---|---|---|---|
| CI01 | average study hours | 5.2 | 4.6 | 5.8 | 120 |
| CI02 | course completion rate | 0.68 | 0.61 | 0.75 | 180 |
| CI03 | average delivery time | 33.5 | 30.2 | 36.8 | 75 |
| CI04 | support ticket rate | 0.052 | 0.044 | 0.060 | 900 |
| CI05 | proportion preferring practice tasks | 0.57 | 0.49 | 0.65 | 150 |
Your Task
Interpret three intervals and write one common misinterpretation to avoid.
Questions
- What is the estimate, and what is the interval around it?
- How wide is the interval relative to the estimate?
- What does that width tell you about the sample size?
- What would happen to it with four times the data?
- Is the target inside the interval?
- What can be concluded about whether the target was met?
- How would you word the figure so the uncertainty travels with it?
Write Your Conclusion
Write the sentence you would put in the document, with the interval included.
Self-Check
- Did I report the interval, not just the estimate?
- Did I read the width before the centre?
- Did I resist concluding on a target inside the interval?
- Does my sentence survive being quoted alone?