Object
This study is about survey questions on happiness using verbal response options, such as ‘very happy’ and ‘fairly happy’. The aim is to estimate what degrees of happiness are denoted by such terms in different questions and languages. These degrees are expressed in numerical values on a 0 to 10 scale, which are then used to compute ‘transformed’ means and standard deviations. Transforming scores on different questions to the same scale allows us to broaden the World Database of Happiness considerably

Method
Native speakers read survey questions on happiness that have been used in their country. For each question separately, they rate the relative value of each of the response options in their language. They do this on a computer screen on which they see a vertical bar scale that they can divide into sections by shifting separation lines. The response options are presented next to the scale and move with the bars. The native speaker’s task is to move the separation lines with the cursor until they feel that the intervals on the scale correspond with the degree of happiness denoted by each of the verbal response options. An example of the scale interval recorder can be seen here.

Judges
University students are invited to take part in this study. Participating professors will recruit volunteers and provide the students a code with which they can use to log on to a website. On this site students are asked to complete the task, which will take about 10 minutes.

Coverage
The aim is to cover 74 languages. Given the precision required we need at least 200 respondents per language, so this study will require the participation of some 15.000 students.

Analysis
This information is used to calculate new averages and standard deviations from the available responses to this kind of questions on happiness in nations. The next step will be to assess whether this exercise adds to the explanatory power of the happiness data. If so, the new values will be entered into the collection of happiness Measures of this database and the present transformed scores will be adjusted automatically.

State by 2022
47 studies have been done in 12 languages. Several methodological papers have been published on that basis. See DeJonge et al. (2017) Diversity in survey questions on the same topic: Techniques for improving comparability.. The available data are stored in the DANS data-archive in the Netherlands under the name The response Scale Transformation Project, direct link https://doi.org/10.17026/dans-zx5-p7pe.

Continuation
The project stagnated since the death of a main investigator, Wim Kalmijn. The available results have not been implemented in the World Database of Happiness because of the still limited number of languages covered. The test for better explanatory power has not been been done because of the limited number of countries covered.
The project is open for continuation by interested colleagues. It is suited for a PhD track.
Contact veenhoven@ese.eur.nl.

Cite as:
Veenhoven, R. (201?)
International Happiness Scale Interval Study
World Database of Happiness, Erasmus University Rotterdam
Assessed on (date) at: https://worlddatabaseofhappiness.eur.nl/related-sources/international-happiness-scale-interval-study/summary-scale-interval-study/