Student #2

The merits of the Likert scale lie in its ability to quickly and cost effectively produce data about attitudes and opinions regarding a product. It can be quickly created and is inexpensive to produce. The Likert scale allows researchers to generate a numerical score based on answers to questions. For example, a researcher may ask if a person agrees or disagrees with a statement and to what extent. The answer to the question is given a numerical value. These values are useful in analyzing large groups of people. The Likert scale does not go into depth with the questions, though, and the researcher is left to figure out what the interviewee might or might not have meant. Differential scales are similar but instead use bipolar concepts, like hard or soft, to figure out attitudes. A numerical score is again given and that score can be used for analysis. Differential scales have the same problems as Likert scales, such as not going into depth with the questions.

Student #3

Research scientists gather data about...

They are measurement tools that use numerical values to rate objects, and are used by researchers who want to cost effectively analyze complex opinions. Likert scales are effective in getting raw data. The score they generate can be used in many business applications and across different demographics. But Likert scales are also flawed in that they are not specific. They do not get the kind of data the questionnaires do, and are therefore less effective in certain situations. Semantic differential scales are fairly similar but not the same. They use a different approach to gather data. Instead of using a range, they use word pairs to get information about material objects and concepts. Differential scales are also cost effective for large population applications, but are limited as well. They do not get data that other research methods might provide.
References

Cooper, D.R. & Schindler, P.S. (2008). Business Research Methods, 10th Edition. New York, NY: McGraw-Hill/Irwin.