
 
To verify the thesis we used GradeStat for 
constructing tables of ARs. AR is the name given in 
(Kowalczyk et al., 2004) to the concentration index; 
it has a representation as an area contained in the 
unit square. AR’s value for a material determines the 
extent to which the material is dissimilar to the 
pattern material in the set of features. The greater the 
|AR|, the greater the dissimilarity between those two 
materials. For simplicity, from now on we use AR 
instead of |AR|. 
We performed this analysis on a subset of the 
population – we considered 37 out of the 56 
materials that were evaluated by the respondents 
(because only for them the respondents estimated the 
time ratio for the level I elements). The set of 
features included 4 features for the time ratios of the 
level I elements (i.e., Introduction,  Main content, 
Summary, and Evaluation). Figure 3 shows the chart 
of ARs, where OX is for materials ordered by their 
average marks, and OY is for the ARs.  
In the figure we can see that the results are quite 
different even in the same groups (i.e., for the same 
marks), but there is a clear trend of descending 
values of ARs for subsequent groups. We can 
conclude that even though it is rather difficult to 
estimate the time ratios for the level I elements in 
the case of e-learning materials (consequently, such 
ratios are not a perfect quality measure for e-
learning materials), the descending trend of the ARs 
and the average ARs makes the ratios a good partial 
measure of the quality of e-learning materials. So we 
decided to replace the four time ratio features with 
one  time_AR feature that says how close the time 
ratios for the level I elements of a given material are 
to the corresponding time ratios of the pattern 
material. 
3.3  Influence of the Correct Didactic 
Structure of an e-Learning 
Material on its Quality 
In this section we will deal with the thesis that 
following the recommendations of traditional 
(paper) learning materials experts (in particular, 
keeping the structure of such materials) is beneficial 
also in the case of e-learning materials, that is, it 
improves their quality. Furthermore, the existence of 
specific elements (identified by experts), the 
assessment of the quality of each such element, and 
the time ratio for the level I elements can be used as 
partial measures for the quality.  
To verify the thesis we analyzed three 
populations of materials. The first population was 
comprised of all the 56 materials evaluated by the 
respondents. The multiplicity of the set of features 
was 40: for each of the 20 elements analyzed in the 
questionnaire we considered both its existence and 
its mark (for the level II elements we considered 
either the marks by the respondents or 0 if there was 
no such mark; for the level I elements we considered 
the average marks based on the respondents’ 
subjective marks for the level II elements). In this 
part of our analysis we did not take into account the 
time_AR feature, because the respondents estimated 
the time ratios only for 37 materials. 
Figure 4 shows the ARs for this population, 
where OX is for the identification numbers of the 
materials that are ordered and grouped by their 
average marks; OY is for the values of the ARs. 
In the chart we can see a descending trend: the 
smaller the average AR, the better the marks of a 
given material. In each of the groups (for subsequent 
average marks) we can clearly see that the results are 
quite different – there are materials for which the 
value of AR strongly deviates from the average 
value in their group. Thus, in the next phase of our 
analysis we took into consideration only those 
materials for which the difference between their 
average mark and their subjective mark is at most 2 
standard deviations; there were 30 such materials. 
We constructed this new population of materials and 
computed ARs for it; the chart is in Figure 5.  
As before, we can see a descending trend: the 
smaller the average AR, the better the marks of a 
given material, but this time the differences between 
the results in each group are much smaller, probably 
because the credibility of the data is greater. Hence, 
we decided to increase the credibility even more by 
constructing a population of only such materials for 
which: (1) as before, the difference between their 
average marks and their subjective marks was at 
most 2 standard deviations; (2) the respondents 
estimated the time ratios for the level I elements; 
there were 20 such materials. The multiplicity of the 
set of features was 41, because we augmented the 
previous set with the time_AR feature. Figure 6 
shows the chart of ARs for that population. 
The charts in Figure 4, Figure 5, and Figure 6 
prove the thesis that the structure of an e-learning 
material has a strong effect on its quality. Therefore, 
we conclude that the existence of specific elements, 
the assessment of the quality of each such element, 
and the time ratio for the level I elements can be 
used as partial measures for the quality. 
The next phase is to select a sufficient subset of 
features that can be used to estimate the quality of e-
learning materials. 
MEASURES FOR ESTIMATING THE QUALITY OF E-LEARNING MATERIALS IN THE DIDACTIC ASPECT
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