Which assay runs can you count?
Separate high scores from scores in valid runs.
The question
A fictional screen marks a candidate for follow-up after a score of at least 50 in two valid runs. A run needs a positive reference from 70 to 90 inclusive and a negative reference of at most 10.
- Run 1
- 56
- Run 2
- 73
- Run 3
- 48
The scores are unitless. The assay owner records the control results.
“Would you count two qualifying runs, and what would settle it?”
Not saved by this site. Your browser may restore text when you navigate back.
A strong answer, step by step
Open each step in turn. This is one strong answer, not the only one.
Step 1: Separate score and validity
What would you do here? Open the move you’d make.
Treat the two raw scores as a provisional count.
The strong move. The follow-up rule applies to a qualifying score from a valid run.
Mark the candidate for follow-up based on the scores alone.
Tempting, but it misses something. The case requires two scores from valid runs. The dashboard omits both controls.
See how a strong candidate says it
“Two scores reach 50. I’d check whether both runs met the control criteria before counting them.”
Why it works: The follow-up rule applies to a qualifying score from a valid run.
Step 2: Ask for both controls
What would you do here? Open the move you’d make.
Check the positive and negative reference against the case criteria.
The strong move. A candidate result counts only after the run meets both conditions.
Check the negative reference alone.
Tempting, but it misses something. The positive reference has its own required range. Both checks must pass.
See how a strong candidate says it
“I’d ask the assay owner for both reference values and the recorded validity of each run.”
Why it works: A candidate result counts only after the run meets both conditions.
Step 3: Apply the controls
The assay owner gives the positive and negative reference pairs. Run 1 is 82 and 7. Run 2 is 52 and 8. Run 3 is 76 and 9.
What would you do here? Open the move you’d make.
Count one valid score at or above 50.
The strong move. The strongest raw candidate score comes from the run with a failed positive reference.
Count run 2 because 73 is the highest candidate score.
Tempting, but it misses something. The positive reference in run 2 falls below the required minimum of 70.
See how a strong candidate says it
“Runs 1 and 3 pass. Run 2 fails because its positive reference is 52. The valid candidate scores are 56 and 48. Only one meets 50.”
Why it works: The strongest raw candidate score comes from the run with a failed positive reference.
Step 4: Give the next decision
What would you do here? Open the move you’d make.
Report the failed control and ask what valid evidence would complete the review.
The strong move. The team gets the specific failed check and the evidence still needed.
Describe A as inactive because the second run failed.
Tempting, but it misses something. The failed control tells you about run validity. It leaves the candidate’s activity open.
See how a strong candidate says it
“I’d leave the follow-up decision open and tell the assay owner that run 2 failed its positive reference. One valid score meets the threshold and the case needs two.”
Why it works: The team gets the specific failed check and the evidence still needed.
The answer, in short
- Decision
- Keep A open and give the assay owner the failed control and valid count.
- Because
- One valid score meets the candidate threshold. The case requires two.
- What would change it
- Another owner-confirmed valid score at or above 50 would meet the case criterion.
Common traps
- Counting the highest score without its controls.
- Treating an invalid run as a biological result.
Check your answer
- I separated score and validity.
- I checked both references.
- I counted only valid results.
- I named what could change the decision.
Last reviewed Nov 11, 2026