Partial Interval Recording

Partial interval recording is an interval recording method. An interval recording strategy involves observing whether a behavior occurs or does not occur during specified time periods. Once the length of an observation session is identified, the time is broken down into smaller intervals that are all equal in length. For instance, a 20 minute observational session may be separated into 2 minute intervals with ten boxes that are used to record the occurrence of behavior. In partial interval recording, the observer marks down whether a behavior occurs any time during the interval by placing an "X" for occurrence and a "O" for no nonoccurrence. A student may engage in a behavior multiple times during the interval or only once for an "X" to be documented.

Partial interval recording means that the observer is interested in behavior that occurs or not in any part of the interval and that the behavior usually does not consume the entire interval. Examples of discrete behaviors that can be observed using partial interval recording include swearing, hitting, participating in class discussions, and making positive statements to peers and others.

Once the recording is complete, the observer counts the number of intervals in which behavior was observed and a percentage of intervals with the behavior is documented. For instance, if a teacher is interested in measuring positive social interaction skills, she may use partial interval recording to measure the percentage of intervals a student is making positive statements such as "way to go" or "good throw." If one or more positive statements were made in three out of ten intervals, then the student engaged in the behavior of interest during 30% of the observational sessions.

A stopwatch or wrist watch is often used to keep track of intervals with a clipboard holding a recording sheet. A tape recording with a sound indicating the end of an interval can also be used to alert the observer and help him or her keep track without having to spend time looking at a timing instrument.

The advantage of the partial interval recording method is that it provides an estimate of frequency and duration of a behavior, and provides information about where behaviors are occurring across observational sessions. A major disadvantage of partial interval recording is that is requires an observer's undivided attention. Teachers interested in this measurement strategy may need to ask someone else to observe and collect partial interval data for them while they are working with students or engaged in instruction. Observing and recording data can be challenging, especially when using a stopwatch since the person recording must attend to both the timing of intervals as well as the student. Partial interval recording documents whether behavior occurred or not but will not provide information about how many times a behavior occurs within the interval. For instance, a student may curse ten times in one interval but only once in another interval. Both intervals will show that the behavior occurred but will not provide information about frequency within the interval.

When the behavior that you are looking at is not easily counted, you can measure the behavior by counting the number of time-intervals in which the behavior occurred. A behavior is not easily counted when:

• It is difficult to tell exactly when the behavior begins or when it ends, or
• It occurs at such a high rate that it is difficult to keep a count on it.

If the behavior happens so quickly that it is hard to catch (the behavior itself does not last for a long time), you may use the partial interval recording method to measure this behavior.