15-minute ratings: During the school day, a principal’s time is a scarce resource. Given the number of observations
they are being asked to do, a mix of long and short observations could help lighten the time burden.
But shorter observations could also reduce accuracy and reliability. To gain insight into the benefits of longer
versus shorter observations, we asked observers to pause and provide scores after the first 15 minutes of a
video and then to record their scores again at the end of the lesson. A randomly chosen half of their observations
were performed this way; for the other half, they provided scores only at the end of the lesson.