## 3 Results
### Students' Opinions towards the Four Teaching Tools--Multivariate Analysis  
We performed the classification of the questionnaire items (the 16 items evaluating the benefits of the four blended learning tools), using the two-step clustering technique, in order to identify the significant predictors among them and their internal connections. The evaluation of the classic oral presentations according to the sixteen items led to the identification of three clusters, the largest one covering 41.0% of the students, the next 37.9%, and the smallest 21.1%. The most important predictor among the 16 items investigated was item 15a: Methods that best help to understand the concepts presented (predictor importance PI = 1.00), followed by item 9a: Clearest way of explaining concepts (PI = 0.98), item 7a: Methods that provide essential information (PI = 0.95), item 14a: Methods that stimulate interest best (PI = 0.95), item 13a: Methods that capture attention best (PI = 0.95), item 16a: Methods that make it easier to learn the concepts presented (PI = 0.92), item 8a: Methods that provide the most accurate information (PI = 0.85) and item 3a: Most useful methods (PI = 0.80); the other items had importance coefficients PI < 0.80. The first cluster identified comprises 37.9% of the students, who strongly agree with the advantages of classic oral presentations. The second cluster (41.0% of cases) contains students who agree to a medium to high extent with the advantages of these methods, and the third and smallest cluster (21.1%) contains students with unfavourable opinions, who agree only to a low to medium extent with the advantages of these methods. The evaluation of PowerPoint presentations according to the sixteen items in the survey led to the identification of four clusters, the largest of which covered 37.4% of students, and the smallest 14.5% of students. The most important predictor among the 16 investigated was also item 15b: Methods that best help to understand the concepts presented (predictor importance PI = 1.00), followed by item 13b: Methods that capture attention best (PI = 0.90), item 14b: Methods that stimulate interest best (PI = 0.86), item 16b: Methods that make it easier to learn the concepts presented (PI = 0.86) and item 9b: Clearest way of explaining concepts (PI = 0.83); the other items had importance coefficients PI < 0.80. The first cluster identified (25.6% of cases) contains the students with the most favourable opinions--who overwhelmingly agree with the benefits of PowerPoint presentations. The second, smaller, cluster (14.5% of cases) contains students who agree to a large extent with the advantages of these methods. The third cluster (37.4% of cases) contains students who agree to a medium extent, and the fourth cluster (22.5% of cases) contains students who agree only to a small extent with the advantages of PowerPoint presentations. The evaluation of the educational videos according to the sixteen items led to the identification of four clusters, two larger ones, each comprising about one-third of the students, and two smaller ones. The most important predictor among the 16 investigated was also item 15c: Methods that best help to understand the concepts presented (importance of predictor PI = 1.00), followed by item 6c: Methods that provide the most expert knowledge (PI = 0.86), item 16c: Methods that make it easier to learn the concepts presented (PI = 0.83) and item 7c: Methods that provide essential information (PI = 0.80); the other items had importance coefficients PI < 0.80. The first cluster identified (32.1% of cases) contains students who strongly agree with the benefits of educational videos. The second cluster (18.7% of cases) contains students who agree to a high extent with the advantages of educational videos.