El agua durante la época Liberal (1870-­‐1940)

As stated at the beginning of section 3.4, the CAM, by [140] , was used in this context, to analyse the students’ responses to the PTPT items in order to determine the collective impact of the use of the VEL, on each of the two student cohorts. The analysis yielded useful results, highlighting interesting themes.

Students’ responses to each item in a test are considered to be the results of the application of their knowledge states for the addressed concept. Each item has associated with it a fragment of the knowledge state required to answer that question correctly. If a multiple-choice item is designed with the knowledge state fragment required to answer it correctly as one of the choices for the item, while the distracters are equally plausible but incorrect and constitute misconceptions, student responses should be concentrated on the correct choice if they are applying the correct knowledge state fragment in responding to the item. However, if students have little knowledge of the concept, their responses may be close to a random distribution among all the choices. As an example, Table 3.4 lists an arbitrary sample set of 100 students' response distributions to a set of 5-choice multiple-choice test item.

Table 3.4: An arbitrary sample set of students' response distributions for test items

(Adopted from [Digironimo, 2007])

0 0 0 0 100 III 5 5 30 10 50 II 20 20 20 20 20 I E D C B A Item Choice Responses Distribution Type 0 0 0 0 100 III 5 5 30 10 50 II 20 20 20 20 20 I E D C B A Item Choice Responses Distribution Type

The way in which the students’ responses are distributed can yield information on the students’ knowledge states. If the students get low scores, their responses are typically either evenly distributed among the different distracters or concentrated on one or two of the distracters. Highly concentrated responses to an item imply that many students are applying a common fragment of the knowledge state associated with the concept; randomly distributed responses indicate less uniformity in reasoning, highlighting possible lack of clue and guessing on the part of the students [137]. The formula and details of the concentration analysis method are given in Appendix B2, while the student cohorts' response distributions to the pre- and post-test items are given in Appendix B3.

The CAM uses a synergy of the Score (S), and the Concentration Factor (C), both of which are functions of the students’ responses, to derive the Students’ Response Patterns (SRPs) for each item in a test. It requires that the pre-test and post-test instruments contain the same items, in the same order. In this context, the post-test contained nearly twice as many items as the pre- test, where all the items in the pre-test were included in the post-test, in addition to other items that assessed the expected learning outcomes. For the purposes of the analysis, pre-test items component of the post-test were extracted, in order, and students’ responses to the items matched against their responses to the pre-test items. The results of the CAM analysis, in terms of the students' S, C, and SRP distributions for the pre-test items and their corresponding post-test items, are highlighted and discussed in Appendix B 3. Table 3.5 presents a summarized view of the results, with respect to the defined SRPs (see [140]), what the SRPs indicate, the number of the SRPs in the UoP and UTON cohorts’ responses to the pre- and post-test test items, and remarks. The remarks relate the indications for an SRP to each cohort’s performance for the items with the SRP.

Table 3.5: Concentration analysis of students' responses to the pre- and post-test items. Students’ Response Pattern (SRP) with respect to a test item Indication UoP Tests Outcome UTON Tests Outcome Remarks No of the SRP in the Pre- Test No of the SRP in the Post- Test No of the SRP in the Pre- Test No of the SRP in the Post- Test HH

Most of the students generally have one dominant knowledge state fragment with respect to the item. This one dominant knowledge fragment the students have is the correct knowledge fragment required to respond correctly to the item

4 7 _{0 4}

UoP: For 4 of the items, most of the students had the

one correct knowledge fragment, before the educational intervention. After the education intervention, the number of items for which most of the students had the one correct knowledge fragment increased from 4 to 7, indicating improved learning.

UTON: Before the educational intervention, there

was no item for which most of the students had the one correct knowledge fragment for the item. After the education intervention, the number of items for which most of the students had the one correct knowledge fragment increased from 0 to 4, indicating improved

learning.

MM

Most of the students generally have either of two dominant knowledge state fragments. Of these two knowledge state fragments that most of the students have, one is the correct knowledge state fragment required to respond correctly to the item, while one is the wrong knowledge state fragment and will lead to incorrect responses to the item.

5 3 _{4 1}

UoP: The number of items for which over 30% of

the students had an incorrect knowledge fragment was reduced from 5 to 3, indicating

improved learning.

UTON: The number of items for which over 30% of

the students had an incorrect knowledge fragment was reduced from 4 to 1, indicating

improved learning.

LH

Most of the students generally have one dominant knowledge state fragment with respect to the item. This one dominant knowledge fragment the students have is incorrect and will lead to incorrect responses to the item.

1 0 _{0 1}

UoP: The one dominant incorrect knowledge

fragments most of the students had for one of the test items, before the educational intervention, was corrected after the education intervention, indicating improved learning.

UTON: For one of the test items, the students had no

dominant incorrect knowledge fragment, before the educational intervention, but the students acquired an incorrect knowledge fragment for the item after the education intervention, indicating reverse learning.

LM

Students have two dominant incorrect knowledge state fragments

Most of the students generally have one of two wrong ideas

1 1 _{1 0}

UoP: The two different incorrect knowledge

fragments most of the students had for one of the items before the educational intervention was not corrected after the education intervention, indicating no learning.

UTON: The two different incorrect knowledge

fragments most of the students had for one of the items before the educational intervention was corrected after the education intervention, indicating improved learning.

LL

Most students generally have one of three or more different knowledge state fragments, somewhat evenly represented among the student cohort. These three or more different knowledge state fragments may or may not include the correct knowledge state fragment required to respond correctly to the item. This often implies that the students generally have no clue and are guessing the answer to the item.

0 0 _{6 1}

UoP: No guessing of responses to any of the test

items before and after the educational intervention.

UTON: The number of items for which most of the

students were guessing without a clue was reduced from 6 to 1, indicating improved

learning. Students became surer of their

Table 3.5, indicates that the usage of the VEL had improved learning impact on both student cohorts, and more especially on the UTON cohort, which reinforces the results of the statistical analysis method. The outcome of the analysis has implications for instruction in that the SRPs inform the instructor of aspects of the addressed concept that require further instructional attention. For example, in Table 3.5, the SRP, LH, did not occur at all in the pre-test response patterns of the UTON student cohort, but occurred once in their post-test response patterns (for the item, Question Q6, in Table B3.2, Appendix B3). This indicates that the instructor may need to further address aspects of the concept represented by that item, for the UTON cohort. Also, the SRP, LM, occurred once (for the item, Question Q6, in Table B3.1, Appendix B3) in the pre-test response patterns of the UoP student cohort, and occurred again (for the same item, Question Q6, in Table B3.1, Appendix B3) in their post-test response patterns. This indicates that the instructor may need to further address issues related to that item, for the UoP student cohort, because of the implication of its repeated occurrence in both their pre- and post-test response patterns, for the same item. The implication is that most of the UoP students had one of two incorrect knowledge fragments about the aspect of the addressed concept represented by the item (Question Q6), and undertaking laboratory activities designed to enhance students understanding of the concept failed to correct the students’ incorrect knowledge fragment for the aspect of the concept.