Measure reaction time
Use ruler-drop trial data to compare reaction times and read the trend: remembering that a faster reaction means a shorter time.
- Read values from a data table: Reaction-time work means pulling each trial's number out of a table before you can compare them.
- Smaller time means faster: A reaction time is how long the response takes, so the smaller number is the faster reaction: the opposite of 'bigger is better'.
Prerequisites are inferred: pending teacher review.
Re-learn the skill with worked practice and clear examples.
To analyze a ruler-drop test, read each trial's time from the table, find the mean, and use the trend: a falling time across trials means the reaction is getting faster.
| | Trial | Reaction time (s) | |
|---|---|
| | --- | --- | |
| | 1 | 0.24 | |
| | 2 | 0.22 | |
| | 3 | 0.20 | |
| | 4 | 0.18 | |
Use the table of one student's ruler-drop trials. What is the student's MEAN (average) reaction time, and what is the trend across the four trials?
Reviewed| | Trial | Reaction time (s) | |
|---|---|
| | --- | --- | |
| | 1 | 0.24 | |
| | 2 | 0.22 | |
| | 3 | 0.20 | |
| | 4 | 0.18 | |
- A.Mean 0.21 s; the reaction is getting faster across the trials
- B.Mean 0.21 s; the reaction is getting slower across the trials
- C.Mean 0.18 s; the reaction is getting faster across the trials
- D.Mean 0.24 s; there is no clear trend
Show the worked solution ▾
Answer: A. Mean 0.21 s; the reaction is getting faster across the trials
- Step 1: Add and divide: Add the four times, then divide by 4 to get the mean. Do the arithmetic from the table values yourself.
- Step 2: Read the order: Compare trial 1 to trial 4. If the times go down as the trials go on, the reaction is getting faster.
Why it's right: The four trial times average to one value, and because the times fall from trial 1 to trial 4, the reaction is getting faster.
- B: The times fall across trials, so the reaction is getting faster, not slower.
- C: 0.18 s is the fastest single trial, not the mean of all four.
- D: 0.24 s is only the first trial, and there is a clear downward trend.
Aligned to HBS 2.1: compute and interpret reaction-time data · reading level ~grade 9
- A lab group averages several ruler-drop trials so one lucky or unlucky catch does not decide their result.
Fill these in as you work through the lesson.
- Reaction time (measured in what units?):
- Stimulus (the cue you respond to (the drop)):
- Trial (one single attempt):
- Mean (average) (add them up, then divide by how many):
- Reflex (is catching the ruler purely automatic?):
In a ruler-drop test, a reaction time means the person responded faster, so a smaller number is .
- A student's three trials are 0.20 s, 0.18 s, and 0.16 s. Is their reaction getting faster or slower across the trials?
- Why do scientists run several trials and use the average instead of just one trial?
- If catching the ruler lower down means a longer time, what does catching it higher up tell you?
A student records ruler-drop times of 0.22 s, 0.19 s, and 0.19 s. Find the mean reaction time, then say whether their reaction is faster or slower than a classmate whose mean is 0.17 s.