Rate
Compare unequal observation periods
Mila makes 9 requests during a 3-minute observation and 18 requests during a 9-minute observation. Every request meeting the definition is counted. The question asks which observation has the higher rate per minute.
Relevant facts
- The observation lengths differ.
- The same response definition is used.
The first observation has the higher rate.
9 ÷ 3 = 3 per minute; 18 ÷ 9 = 2 per minute
The second observation has more requests in total and fewer requests per minute. Compare the two rates using the same units.
Percentage
Keep prompted responses out of the numerator
Across 15 eligible opportunities, a learner responds correctly without a prompt on 9, correctly after a prompt on 4, and does not respond on 2. The measure is percentage of opportunities with an independent correct response.
Relevant facts
- All 15 opportunities belong in the denominator.
- Only 9 qualify as independent correct.
Record 60% independent correct.
9 ÷ 15 × 100 = 60%
Use the 9 independent correct responses as the numerator and all 15 eligible opportunities as the denominator. The four prompted responses and two opportunities with no response remain part of the opportunity count.
Mean
Summarize three latencies
Three measured latencies are 12, 15 and 9 seconds. Each begins at the same defined cue and ends at the same defined response.
Relevant facts
- There are three measurements in seconds.
- Their sum is 36 seconds.
Mean latency is 12 seconds.
(12 + 15 + 9) ÷ 3 = 12 seconds
The mean is neither the total time nor evidence that every response began after exactly 12 seconds.