Likert scales

Using existing scales. With thousands of Likert scales (Likert, 1932) reported in the research literature, it is tempting to see a scale and decide to use it for measuring some indicator instead of developing a new one. Your decision depends on several factors. First, as the investigator, you will need to show that the scale, including the statements it contains and the response categories, are appropriate in terms of the culture of the group being studied. Will the respondents you intend to collect data from understand the statements? Do the statements have meaning in terms of the local culture? Would any of the statements raise serious social, political, religious, or other issues? Would a statement be seen as foolish?

In research terms, you would be testing of content validity of the items. Applying these kinds of criteria may lead you to abandon use of an existing scale, but in the process, you may see ways of adapting at least some the statements and response categories for use in your setting. This is what Tessler (1987) did in a study of religious conservatism and opinions about the effectiveness of the government in serving citizens in Tunisia. Scales for both measures existed in the research literature but were not suitable for use with the population he was investigating. He modified the scales and tested them for validity and reliability with Tunisian samples before using the scales in his investigation (Tessler, 1987, pp. 141-144).

Second, in using an existing scale, a researcher has to demonstrate convincingly that the scale is a valid and reliable measure for the variable being studied. Evidence offered for validity and reliability by the developer of the scale is not sufficient. A scale developed in Europe or North America, for example, may be valid and reliable for use there, but not in other regions of the world. Therefore, the first requirement is to establish that the scale is valid and reliable for its intended use. Any of the commonly used methods described in Chapter 6 can be used for this purpose.

Whether you modify an existing Likert scale or construct a new one, the steps are the same. As with every measuring instrument, the first step is to analyze the concept being studied to determine if it has one or more dimensions and to identify and describe the dimensions you intend to measure. Construction of a scale starts with the selection of statements to serve as indicators of a concept or one of its dimensions.

Selecting statements. Scales are based on a number of items, usually in the form of statements that express on opinion or view regarding the variable being measured. Statements can be taken from a variety of sources. As mentioned before, existing scales can be a source of statements. You may discover these in the course of reviewing the literature. Brief exploratory research, based on interviews with persons who have different views on the topic you are researching, can produce a range of useful statements. Focus groups are a good source of items (Altareb, 1997). Statements may also be based on comments you hear or opinions expressed in newspaper or magazine articles.   You can also draw on your own experience in preparing statements.

It is a good idea to assemble as many statements as you can. Only clearly favorable or unfavorable statements   about the issue in question should be used. Statements should also represent different levels of feeling about the issues. Some questions should express mild positive or negative views, while other should express increasingly stronger views in each direction. Do not use neutral statements. They will not differentiate between persons with different views on whatever you are measuring. A few other guidelines for writing items are listed in Box 7.2.

Using these guidelines, examine the statements you have assembled. Eliminate questions that are not clear, do not express a clear positive or negative opinion, or that are too much alike.   At this point, it is also a good idea to check to make sure each statement reflects some aspect of the dimension you want to measure. As a further check, ask several fellow students or informed persons to evaluate the items for unidmensionality and for face or content validity. Each reviewer could be asked to rate each question as "very appropriate," "appropriate,"   "inappropriate" or "completely inappropriate." Depending on the kind of items being tested, another set of judging categories could be used.   Keep only the items that a majority rated as clearly appropriate.