*4.3. Reliability of the Collected Data*

Analysis of the collected data also revealed that only a quarter (27.16%) of the respondents moved all 13 sliders provided in the VAS matrix. It means that three-quarters of the respondents evaluated less than 13 criteria during the experiment. Since all the responses where single and more criteria are assessed contribute in the construction of the data matrix *R* (Equation (1)), it is necessary to make sure that the data collected during the survey can be trusted.

Both the Cronbach's Alpha and the Split-Half techniques (with Spearman and Brown correction) were employed to determine the internal reliability of the collected data. The calculated value for the *Split-Half technique* was 0.9772, and the total *Cronbach's Alpha* reliability coefficient was 0.9861 (Table 4). It means that the overall internal reliability of the collected data is very high. Cronbach's Alpha for all the 13 criteria also showed very high reliability (0.9189 to 0.9494). It is assumed that internal data reliability is appropriate if the value of the Alpha coefficient/ is at least 0.7.
