When to use it
In momentary time sampling (MTS), you look at the client only at the moment each interval ends and record whether the behavior is happening at that instant. You ignore what happens between checks.
Use it when:
- The behavior is ongoing or lasts a while, such as on-task behavior, engagement, sitting in a group, or social play.
- You are also doing other work, such as running a group or teaching, and can’t watch continuously.
- You want to check several clients in turn. When MTS is used for a group, recording how many group members are engaged at each check is often called PLACHECK (planned activity check).
MTS can either overestimate or underestimate the true amount of behavior. The error is not in a predictable direction, and it grows with longer intervals. Brief, low-rate behavior, such as a single hit, is often missed entirely. Don’t use MTS for short behaviors that are over in a second or two.
How to fill it in
- Write the operational definition at the top of the sheet. MTS works best with a behavior you can judge at a glance. Example: “On-task: eyes directed at the teacher or assigned materials, or actively working on the assigned task.”
- Choose the interval length and write it on the sheet. Common choices range from 30 seconds to several minutes, depending on the behavior and how much else you are doing. Shorter intervals give better estimates. Practice varies.
- Write the scheduled check times in the Time column before you start, or use a timer that signals each check.
- At each signal, look immediately and record + if the behavior is occurring at that moment or - if it is not. Record what you see at the instant of the signal, not what happened a few seconds before or after.
- If you miss a check, mark X and leave it out of the calculation. Don’t fill it in from memory.
- For group checks, use one column per client, or write the number of group members engaged out of the number present.
Common mistakes:
- Scoring based on what happened during the interval rather than at the moment it ended.
- Glancing “sometime around” the signal. Late checks bias the data.
- Using long intervals for behavior that changes quickly.
The sheet
Client(s):Date:Observer:Setting / activity:
Target behavior and definition:
Interval length:Start time:
Code: + occurring at the moment of the check | - not occurring | X check missed
| Check # | Scheduled time | Client 1 | Client 2 | Client 3 | Notes |
|---|---|---|---|---|---|
| 1 | |||||
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| 20 | |||||
| Total + / checks | |||||
| Percent of checks |
Summarizing the data
Percent of checks = number of checks scored + divided by number of checks completed, times 100.
Worked example: a 40-minute group activity with 2-minute intervals gives 20 checks. Client 1 was on-task at 13 of the 20 checks.
- 13 / 20 x 100 = 65% of checks
Report this as “on-task at 65% of 2-minute momentary time samples.” Treat it as an estimate of the proportion of time on-task, not an exact measure.
For a group check: if 4 of 6 students present are engaged at a check, that check is 67%. Average the percentages across checks for the session.
Tips
- An interval timer that vibrates is much easier to use than watching a clock, especially while teaching.
- Pair MTS with a brief continuous measure now and then (such as a few minutes of duration recording) to check that the estimate stays reasonable.
- For IOA, compare checks one at a time. Both observers must use the same signal so they look at exactly the same moment.
- If a behavior of interest is brief and important, such as aggression during group, track it separately with frequency recording. MTS will not capture it reliably.