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Thurstone scales are used in measuring opinions. When investigating people’s attitudes towards some specific topics, there must be a way to quantify the responses obtained from the respondents so that the responses can be compared and analyzed.

Over time, several methods for quantifying respondents' attitudes have been developed and one of the most effective of these methods is the Thurstone Scale.

What is a Thurstone Scale?

The Thurstone Scale is a unidimensional scale that is used to measure and quantify people's opinions and attitudes in a survey. In the design of the survey, the agree-disagree question format is usually employed.

The researcher will assign numerical values to the agree-disagree statements so that he/she can easily understand the opinions of the respondents on a topic and also grasp the strength of that opinion. The numerical value assigned will explain whether the respondent’s responses to the topic are favorable or unfavorable.

Also referred to as the method of equal-appearing intervals, the Thurstone scale in an experiment, offers an effective and accurate way of measuring opinions and a more effective way of drawing statistical comparisons. The Thurstone Scale is commonly used in the Sociology and Psychology fields.

It was also the first formal method of measuring attitude in these two fields with a history that goes as far back as to the early 20th century. Developed by L.L. Thurstone, the scale was initially used in religion before it became famous in the Sociology and psychology fields.

It is clear that the primary purpose of the Thurstone scale survey is to measure attitudes, but could it be that it has other usefulness? Let us find out.

Learn About: What is a Survey Rating Scale? + [Types & Question Examples]

What is the Purpose of the Thurstone Scale?

The purpose of the Thurstone scale survey is to measure the attitudes and opinions of the respondents on a specific subject. 

However, the scale can also be used to measure a wide range of market research surveys, such as

Market surveys that measure opinions: The Thurstone scale survey question provides quantifiable data about the measured strength of the respondents' behavior and opinions.

Market surveys that gauge attitudes or feelings: The Thurstone scale makes use of the customer satisfaction reports to predict future purchasing trends. It also uses the employee engagement level to calculate the organization’s potential turnover.

Use For Free: 11 Market Survey Template + [Question Examples]

Characteristics of Thurstone Scale 

The Thurstone scale survey has unique characteristics, some of which are:

1. The mean or median must be calculated: Since each option in the survey question is weighted, the mean or median of each of the options must also be calculated. This calculation will form the basis or standard of the selection method to be used in the final survey.

2. The scale involves two steps: One important characteristic of the Thurstone scale survey question is that it is never applied at the first iteration stage without the judges' ratings. The options visible to the respondent are weighted, and a consensus is reached on whether they should be there in the survey.

3. There are only agree or disagree options: The respondent to the survey questions can only select based on their agreement or disagreement with the statement. 

Read: Bad vs Good Survey Questions + [11 Examples]

How to Interpret the Thurstone Scale

When you are responding to the Thurstone scale surveys, remember that the respondents are expected to either agree or disagree with the statements.

Once you have received all the responses, go ahead and sum the median scores of each of the statements your respondents agreed with. After this, simply divide the result by the number of statements they ticked.

If, for example, a respondent checked agreed with five statements which have median scores of 3.5, 7, 9.5, 4, and 10, the attitude score of that respondent will be (3.5 + 7 + 9.5 + 2 + 9) / 5 = 6.2. 

Remember that the measuring scale is from 1 to 11, and this respondent’s score is just above the midpoint of the standard scale. From the score, the researcher can conclude that the respondent’s attitude is a fairly favorable one towards the topic in question.

If you are calculating a larger set of data that has hundreds of numbers (which is not likely to happen with surveys), you may find it more difficult to determine what the median score is. If this happens, use the following median formula:

So, you as the researcher can simply assign each answer that is “agree” or “yes” a score of 1 to 11. 

Be sure the score you assign to the statements is based on the above scores. Now, for each answer that is “no” or “disagree”, assign a score of 0. 

Whatever the total score of each graded question is, will represent the strength of the respondent’s opinion. Any respondent with a higher score can be assumed to have a more supportive opinion.

The last stage will be to evaluate and compare your results. The Thurstone scale has made these processes easier because it represents attitude with a number value. You can use the average score of the groups to compare the attitudes of individuals or groups.

That is the step-by-step process of how to calculate and interpret your survey manually, but if you don’t find maths and statistics fun, you can simply use Formplus Analytics to compute your results in seconds and get your final result

Advantages of a Thurstone Scale

  1. The Thurstone scale allows you to write as many statements as you want. This means you can include as many statements as possible to support your research.
  2. You can be assured of your survey reliability because the judges that will rate your scale are highly knowledgeable.
  3. The Thurstone scale provides the average score of your survey ranks. This assists the researcher when analyzing the results from the respondents because the researcher already knows what score to compare the result to.
  4. The scale also gives the researcher the monopoly to choose items that represent the desired range.

Disadvantages of a Thurstone Scale

  1. The Thurstone scale is time-consuming. This is because the questions are created and administered in two tedious steps that involve lots of time.
  2. The scale is complex. Many people that use surveys want to easily create some questions, distribute them to respondents, analyze the results, and draw conclusions. Nobody wants to calculate the median or deal with some other “complex” mathematics obtainable on the Thurstone scale.
  3. There is no sure method of measuring attitude; we only try to measure the expressed opinion and then draw inferences from it about people’s actual feelings or attitudes.
  4. Limited answer options. With the Thurstone scale, there are no in-between, just two options. Either you agree or you disagree.
Learn About: The 4,5, and 7 Point Likert Scale + [Questionnaire Examples]

Thurstone vs Likert Scale

The Likert scale was born out of the Thurstone scale four years after the invention of the latter. The aim of developing the Likert scale was to simplify the complex Thurstone scale and ensure that it is more reliable.

The major differences between the two scales are that while the Thurstone scale has a complex scoring system, and time-consuming developing format, the Likert scale is simplified, and has less development time. Also, unlike the Thurstone scale that requires the intervention of intermediary judges, which can be often biased and unreliable, the Likert scale doesn't require interventions and is rather more reliable.

Use for Free: 13 Likert Scale Templates + [Questionnaire Examples]

Thurstone vs Guttman Scale

The Thurstone scale is decided by the judges on a scale of 1-10 by calculating the mean and the median. The Guttman scale, however, is decided by expert judges who would individually submit how they agree with the different statements. The last agreed statement submitted by the experts will indicate whether they agree with the previous statements.

The survey questions in the Thurstone scale survey are decided by attributing relative values to each of the statements. On a Guttman scale, the survey questions are decided by the average degree of agreement for each of the statements. Where there is the least agreement on a statement or statements, the statements will be taken out of the survey.

The Thurstone scale deciding standard ranges from extremely unfavorable to extremely favorable, while the Guttman scale deciding standard ranges from Yes/No and agreement to disagreement.

Either median or mode is used for analyzing the Thurstone scale, while the average of opinions is considered for analyzing the 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 the Guttman scale will be in terms of difficulty in execution and also similar to the Thurstone scale, each judge or group of judges can interpret the statements differently. This can lead to a margin of error in the collected information.

Examples of the Thurstone Scale

When the Thurstone scale is used in a survey, a series of related statements on a particular topic will be set up. For better understanding, here are a few questions that reflect the way statements in a Thurstone scale survey are set:

Example 1

With the use of Formplus builder, a Thurstone scale survey was created for some high school students. The aim of this survey is to measure the attitudes and opinions of the students concerning groups and group activities.


Example 2

This second example is a bit more detailed and survey-like.

This example focuses on developing a Hepatitis-B attitude scale, the following statements can be developed to drive out the statements. This form is also created with Formplus Builder.


All of these questions only have the agree or disagree options, which means you can either agree with a statement or simply disagree.

(Note that, it is best that your survey questions are at least 20 or more)

Conclusion

Normally, the process of comparing the opinions and attitudes of the respondents on a topic can be difficult. Any researcher who has attempted or tried to create the study design for the study, perform the analysis, and also present the data from the experiment in paper or a report can attest to the level of difficulty the paper approach can pose.

The Thurstone scale helps the researcher to eliminate some of these difficulties by developing a method that helps you quantify and compare the responses with much less effort.

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