Define Likert Scale and Thurstone Scale.
It is a method of ascribing quantitative value to qualitative data, to make it amenable to statistical analysis. A numerical value is assigned to each potential choice and a mean figure for all the responses is computed at the end of the evaluation or survey and is used mainly in training course evaluations and market surveys, Likert scales usually have five potential choices (strongly agree, agree, neutral, disagree, strongly disagree) but sometimes go up to ten or more. The final average score represents overall level of accomplishment or attitude towards the subject-matter.
It was one of the first and most productive scaling theorists. He actually invented three different methods for developing a one dimensional scale, the method of equal-appearing intervals the method of successive intervals and, the method of paired comparisons. The three methods differed in how the scale values for items were constructed, but in all three cases, the resulting scale was rated the same way by respondents. To illustrate Thurston’s approach, I’ll show you the easiest method of the three to implement, the method of equal appearing intervals.