Cumulative scale (Guttman)
The cumulative scale or Guttman scale measures to what degree a person has a positive or negative attitude to something. It makes use of a series of statements that are growing or descending in how positive or negative a person is towards the subject. If for instance on a scale with seven statements the respondent agrees with the fifth statement, it implies that he or she also agrees with the first four statements, but not with statement number six and seven.
To create a Guttman scale, you need to:
- Determine the focus: what concept are you going to measure (see what people's attitudes are toward it)?
- Ask a group of people (or a person) to write down different statements about this concept, reflecting different opinions or attitudes about the subject. Make sure you have a large number of statements, making sure that people can either degree or disagree with them (no - open - questions for instance).
- Rating the scale items: the next step is to have your judges rate each statement, indicating whether the statement expresses a positive (favourable) or negative (unfavourable) attitude towards the concept. The members of the group must not express their own opinion about the concept, they must only indicate whether the statement is favourable or unfavourable.
- Developing the scale: construct a matrix or table that shows the responses of all the respondents on all of the items. Then sort this matrix so that respondents who agree with more statements are listed at the top and those agreeing with fewer are at the bottom. For respondents with the same number of agreements, sort the statements from left to right from those that most agreed to those that fewest agreed to.
- If there are lots of items, you need to use a data analysis called scalogram analysis to determine the subsets of items from our pool that best approximate the cumulative property. Then review these items and select the final scale elements. There are several statistical techniques for examining the table to find a cumulative scale.
- Because there is seldom a perfectly cumulative scale you usually have to test how good it is. These statistics also estimate a scale score value for each item. This scale score is used in the final calculation of a respondent's score.
- For a detailed example, see http://www.socialresearchmethods.net/kb/scalgutt.php
You can now use the scale to measure attitudes 'in the field': enter the list of statements and use them to interview people or present them in a document. For each item, they should express whether they agree or disagree. Each scale item has a scale value associated with it (obtained from the scalogram analysis).
To compute a respondent's scale score we simply sum the scale values of every item they agree with.
On the Scoring tab:
- Score values box: list the different statement to which the respondent can agree or disagree. Then enter a scoring value for each statement.
- Scoring: see the page on this topic
- Number box: select the number of decimals for the total scoring value of the baseline/targets.
- Choices box: By default, agreement is expressed by ‘Agree’ and disagreement with ‘Disagree’, but you can change these options here.
On the Targets tab:
- For each statement, click in the checkbox of the ‘Agree’ or the ‘Disagree’ column. The total scoring value is shown at the top of the column.
- When you measure at beneficiary level, specify which percentage of the target group you expect to reach that target. On the bottom row Logframer will calculate the total scores for the target population.