Some may not like it
Others may feel nervous
It is a source of unwarranted information
Others may feel their professional competence is being questioned.
The likes and dislikes of the learner
General characteristics of the learner
The learner in the teaching environment
The teacher's perception of the learner
You want direct information
You are trying to understand an ongoing behavior, process, unfolding situation, or event
There is physical evidence, products, or outcomes that can be readily seen
Written or other data collection methods seem inappropriate
Large amounts of data needs to be collected quickly
Here's an interesting quiz for you.