There are three different types of response systems: show of hands, lettered signs, and electronic.
Show of hands is not recommended because:
(1) it is difficult to know when to call the question,
(2) it is difficult to gauge the relative numbers of votes for the various answers when they are called serially,
(3) it is difficult to tell whether all students are participating,
(4) many students will only participate with less exposure, and
(5) some students will identify a strong student and simply raise their hand at the same time.
Lettered signs are user friendly, inexpensive, and allow considerable privacy when displayed at chest level. Color coding helps the instructor to assess the distribution of answers in a large class. A blank back, or a back with random other answers, prevents students from copying those in front of them. Simple signs with 4 answers can be prepared by printing large letters on half pages of colored paper, gluing these half pages to the top and bottom of each side of an intact sheet of paper, inserting the whole into a sheet protector, and taping the opening of the sheet protector closed. These signs can go into students' ring binders and hold up well over the year.
Electronic response systems have become more user friendly and more
economical as "clickers" have replaced hard wired systems. Electronic systems
remain more expensive than lettered signs, but have the advantage of providing
more quantitative data. The main disadvantage is that projection has to be dedicated
to messages allowing the students to check that their signal has been received.