When in a lab/shop situation and a series of tasks, measurements or observations are to be performed, especially where they must lead to a conclusion or a recomendation, I have found it to be most helpful to prepare and assign a "worksheet" that provides a directed and structured method of the tasks to be performed. The students individually OR in a team may work independantly of the instructor and decide and report their OWN observations/conclusions as directed by a well-prepared "worksheet". This has the added advantage of allowing the instructor to oversee the entire class as opposed to concentrating on any one group or individual and therby, leaving the rest of the class in limbo.