Unknown outcomes produce an honest range
If some outcomes are unknown, you can report the rate among known outcomes and a possible range for everyone. These are different statements.
In 100 registrations with 60 passes,20 failures and 20 unknowns, the observed-outcome rate is 60/80=75%. For all 100, the pass rate is at least 60/100=60% and at most 80/100=80%. Unknowns do not automatically become failures or successes.
Use the denominator appropriate to the stated question. Label 75% as the rate among known outcomes, and show missingness and bounds when discussing all registrations. Such bounds express logical possibilities from unknown outcomes, not statistical confidence intervals.
Source: W5 PDF pp. 3-51, 53. The lecture uses both a constructed 200-student support example and a synthetic 4,665-registration course dataset. They are different tables with different units.
The mean of complete 0/1 outcomes is a rate. The denominator is course registrations, linking directly to the later lecture on counts and rates.
Practice problems
Supplementary study questions on the lecture concepts — not verbatim exam questions. Each answer counts toward spaced review.
1. Conceptual understanding
Definitions and distinctions.
With 60 passes, 20 fails and 20 unknowns, what is the known-outcome pass rate?
What are full-population pass-rate bounds for 60 passes, 20 fails and 20 unknowns?
2. Application
Apply the concept to a case or calculation.
There are 30 passes,10 fails and 10 unknowns. What is the known-outcome denominator?
For that 50-case dataset, what is the all-case lower pass-rate bound?
3. Interpretation and limitations
Evaluate assumptions and justify conclusions.
For the same dataset, what is the all-case upper bound?
Are these unknown-outcome bounds a confidence interval?
Explain it in writing
Self-checked, not marked. Write a few sentences, then compare with the example answer. Your writing is saved as you type.
Show an example answer
Its denominator includes 20 unknown outcomes. It is the lower bound for the full population, assuming all unknowns fail. The known-outcome denominator is 80.
Check: did you answer the question, use evidence or working, and avoid claiming more than the evidence supports?
Show an example answer
The outcome becomes known, reducing the number of unresolved cases. This narrows the gap between the lower and upper bounds.
Check: did you answer the question, use evidence or working, and avoid claiming more than the evidence supports?