Thurstone vs Guttman scale

Attitude measurement is an important parameter to understand the thoughts and opinions about a target sample. Attitude measurement surveys have been successful in gaining feedback on respondents attitudes about the topic under discussion. These surveys are carefully curated with structured question types and scales.

This is where attitude scales come into the picture. Scales are used to associate a numerical value with respondent behavior and thoughts. It is possible to have a number corresponding to attitudes only when the attitude is considered accountable on only one scale (uni-dimensional scale).

These scales can be classified into: Nominal, Ordinal or Interval scales and practically, there is a well-constructed process for attitude scaling such as Likert, Guttman, Bogardus or Thurstone. Thurstone and Guttman scales are two of the most distinctive attitude measurement scales of all used to refer respondent behavior in real-life phenomenon with observation-based research.

Thurstone scale was designed by psychologist Robert Thurstone in an attempt to equate interval scale of measurement with the attitude scale and introduce a scale with statements appearing at equal intervals. While Guttman scale is a cumulative scale developed by Louis Guttman in 1944 – 1950 used to analyze the continuum for the topic of research, i.e., if in a list of 10 questions, if the respondent agrees to the 8th statement – it depicts that he/she agrees with the preceding questions as well and does not agree with the 9th and 10th statements.

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How to construct a Thurstone Scale?

Predicting results and setting comparison of various feedbacks is much more convenient than attempting to quantify something as intricate as respondent attitudes. Thurstone is a systematic technique to perform the process of differentiating and forecasting results.

Thurstone scale was traditionally implemented in sociology and psychology. It is constructed by taking multiple “agree-disagree” statements with values corresponding to each of these statements. Thus, Thurstone scale is used to ascertain respondent opinions and feelings and the intensities of those respective opinions.

Learn more: Nominal Scale

There are four main steps of constructing a Thurstone scale:

Step 1: Gather statements regarding the topic in-hand which will possibly have a broad scope of responses  – usually from extremely unfavorable to extremely favorable.

For example, if a researcher intends to learn about opinions related to Trump’s win in the presidential elections, he/she needs to accumulate a list of statements –

  • It is one of the most skewed results in the history of U.S elections.
  • It is unfair that Trump won the elections despite the rampant hate for him among citizens.
  • It is disappointing to see Trump being appointed as the U.S President.

Step 2: Statements that do not contribute towards the objective of research can be discarded. The ones that are selected are then sent out to a group of people/judges for further filtration.

Step 3: These judges then segregate the statements on a 1-11 scale where 1 indicates extremely unfavorable and 11 indicates extremely favorable. Sections of statements are created – extreme sections will have the most disagreed and the most agreed statements and the midsection will have statements which are neither unfavored or favored. Judges are expected only to stack extreme statements and the midpoint. The distance between this ordinal data is assumed to be equidistant while analyzing.

Each statement is to be rated in terms of overall favorability and not on the basis of personal inclinations.

Learn more: Ordinal Scale

Step 4: Every statement will have a rating on the 1-11 scale. This number corresponding to each statement will be an average of the ratings provided by multiple judges. The statements which can’t be rated by the judges are usually not considered for further analysis.

Sr. No Scale Statement Scale Score
1 It is one of the most skewed results in the history of U.S elections. 8.2
2 It is unfair that Trump won the elections despite the rampant hate for him among citizens. 5.9
3 It is disappointing to see Trump being appointed as the U.S President. 9.5
4 It is the best thing that has happened in the U.S politics. 5.5
5 Trump has been a believer of world peace and he will surely work towards it. 1.8
6 Trump believes in racial equality. 4.3

After discussing all the statements and eliminating undesired ones, a final list of statements for Thurstone scale can be created. This scale can then be sent out to the target audience in order to compare and predict the results.

For example, in the above example, the least rate statements are the least favorable by the judges. If the respondents are of the opinion that they favor statements number 1, 3 and 5,  the Thurstone score will be = 8.2+9.5+1.8/3= 6.5

Thus, Thurstone score = Values related to the statement favored by respondents / the total statements were chosen by respondents

Learn more: Interval Scale

How to construct a Guttman Scale?

In many cases, the strength of respondent opinions is more important than the opinions themselves. Guttman scale, also popularly known as cumulative scale, has a series of statements chosen by a careful rating process. From this list of statements, it is subsumed that a respondent agrees particular item also chooses to agree with the preceding statements.

There are multiple grievous issues where it is important to know the strength of respondent opinions as opposed to just their opinions. Guttman scale project the severity of the opinion by including a list of dichotomous questions in terms of “agree-disagree” or “yes-no”.

Guttman scale question is used in various surveys –

  1. To analyze cumulative studies
  2. To gauge respondent behavior and feedback
  3. To collect information about customer and employee feelings

This cumulative scale has been used in understanding customer satisfaction and also employee engagement.

To explain the process of constructing a Guttman scale, we can take the above-mentioned example – Trump’s win in the presidential elections. Ever since Trump’s success at the elections, the U.S has been divided into two sections – one that fathoms Trump for all his endeavors and one that criticizes him for his every move.

A Guttman scale can be developed by following the below mentioned steps.

Step 1: Have a defined purpose of using Guttman Scale: For any scaling technique to be productive, the purpose of constructing it should be well-defined. In the example under discussion, the researcher must decide the intent of having statements related to Trump in the survey.

Step 2: Note down a series of statements: A researcher can obtain impactful insights into the value of the statements only if there are various statements related to Trump.

    1. It is one of the most skewed results in the history of U.S elections.
    2. It is unfair that Trump won the elections despite the rampant hate for him among citizens.
    3. It is disappointing to see Trump being appointed as the U.S President.
    4. It is the best thing that has happened in the U.S politics.
    5. Trump has been a believer of world peace and he will surely work towards it.
    6. Trump believes in racial equality.

It is advisable to create a list of 80-100 statements before getting them evaluated by judges in order to receive accurate results.

Step 3: Assign values to every statement –  The list of 80-100 statement has to be rated by subject matter experts. Each one of these experts is supposed to rate every statement. The experts are expected to submit their agreement or disagreement with the mentioned statements. This feedback should not be governed by their personal opinions and should rather be in favor of the study.

Learn more: Rating Scale

Step 4: Format the statements for analysis: This step is critical for research. The statements are usually produced in Matrix format.

Respondent Statement 1 Statement 2 Statement 3 Statement 4 Statement 5 Statement 6 Statement 7
2 Yes Yes Yes Yes Yes Yes Yes
12 Yes Yes Yes Yes
18 Yes Yes Yes Yes Yes
21 Yes Yes
25 Yes Yes Yes
30 Yes Yes

In the matrix above, in the first row, if someone agrees to statement 7, it indicates that the individual must have agreed to all the statements before that, i.e. – statement 1 to statement 6.

There certain exceptions in the rating process but usually for those respondents who agree to statement 5 would have agreed to the statements that lead up to it  – i.e., 1 to 4.

Data analysis with a limited number of statements and the target audience is easy but when a considerably large data is collected, it becomes important to conduct careful analysis. In that case, marketers are expected to analyze a subset that is closest to the desired cumulative.

Learn more: Guide to Market Research Surveys

Various statistical methods can be used for the analysis purpose of this scale and the quantitative data collected can also have representative values while calculating.

Step 5: Decide the Guttman scale – On the basis of the judgment by experts, those statements with the least agreement can be eliminated from the final scale and a filtered list of statements can be sent to the respondents. Respondents are supposed to submit their agreement or disagreement with the final statements.

For the example of Trump winning the elections, the order of the statements can be as mentioned below:

  • It is disappointing to see Trump being appointed as the U.S President.
  • It is unfair that Trump won the elections despite the rampant hate for him among citizens.
  • It is one of the most skewed results in the history of U.S elections.
  • It is the best thing that has happened in the U.S politics.
  • Trump has been a believer of world peace and he will surely work towards it.
  • Trump believes in racial equality [can be kept out of the scale]

Researchers can compare the various degrees of agreement/disagreement with all the group of respondents. A high Guttman score depicts higher agreement towards the statement and a lower score depicts lower agreement.

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Thurstone vs Guttman Scale

Thurstone Scale Guttman Scale
The scale is decided by experts on a scale of 1-11 using mean/mode. The scale is decided by experts as they submit their agreement with the various statements and the last agreed statement indicates that they agree with the previous statements.
Thurstone scale survey questions are decided by assigning relative values to the statements. Guttman scale survey questions are decided by the average degree of agreement for each of the statements. In case of least agreement, the statements will not be a part of the survey.
The standard of deciding Thurstone scale is from extremely unfavorable to extremely favorable. The standard of deciding Guttman scale is from agreement to disagreement or Yes/No.
Either median or mode is used for analyzing Thurstone scale Average of opinions is considered for analyzing Guttman scale
The only limitation of the Thurstone scale is that as corresponding values are allotted as per the understanding of a judge or a group of judges are non-uniform, the mathematical calculations can be inaccurate. The limitation of Guttman scale will be in terms of difficulty in execution and also similar to Thurstone scale, each judge or group of judges can interpret the statements differently – which can result in margin of error in the collected information.