For validation, the pre-test, post-test and the observation schedule were given to three experts in Physical Science in the Ehlanzeni Region of education in the Mpumalanga province of South Africa to read and make corrections and suggestions. This is to ensure both face validity and content validity. Two of these experts have been teaching Physical Science in the high school for six and eight years respectively. They both hold B.Ed. degrees in Science education. One was the head of Science department and has six years’ experience of teaching Physical Science. The second teacher at the time was a principal of a high school and had eight years’ experience in teaching Physical Science in a high school as well. The third expert was at the time the Curriculum Implementer (CI) of Physical Science in the Ehlanzeni region of education. These three experts made valuable suggestions on the test as follows:
Question one of part 1 had its multiple choice answer (b) being; the direction of the switch. It was suggested that this option should change to, the switch. The reason being that a switch has no direction and may mislead or confuse the learners.
The phrase, “the north pole of” or “the south pole of” was suggested to be inserted in question 4 of part 1. This was to prevent the question from having two of the multiple choice answers from being the right answers. These two options were options (a) and (b).
Question sixteen of part 1 had a multiple choice option reading “the magnetism is turned off”. It was changed to “the magnetism is lost” for the clarity of that multiple choice option.
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Originally, all the questions in part 1 had option (e); none of the above. But this option was removed from the options of all the questions entirely. As stated by Gay & Airasian, (2003: p. 152) “when constructing a test, one must avoid options like none of the above or all of the above”.
The three experts agreed that the test adequately measures all the learning outcomes or objectives of the topic electromagnetism in grade 11 Physical Science. On the observation schedule, there was no correction or suggestion made.
The structured questionnaire was also given to these three experts mentioned above to read and answer. They were also requested to make suggestions regarding omissions, ideas that may be important and that may have been left out and those ideas that should be removed. There was a concern of clarity of one statement on the questionnaire. The statement reads; “ICT usage makes teaching very descent”. It was therefore suggested that the word descent be clarified or the statement removed. Hence the statement was removed for lack of appropriate word or phrase to simplify the statement.
In addition to these views of the three experts, the questionnaire was given to the pilot sample and their teacher for pre-testing. The pilot sample was also encouraged to make suggestions to improve clarity of the statements in the questionnaire. But this time, no comments or suggestions came up even though the researcher was present at the time to pick up problems and suggestions regarding clarity and ambiguity of the statements in the structured questionnaire.
3.5.2 RELIABILITY OF THE INSTRUMENTS
Reliability tells test users about the consistency of the scores produced in a test and Validity tells test users about the appropriateness of a test. Both are therefore important for judging the suitability of a test or measuring instruments (Gay & Airasian, 2003: p. 141). However, (Gay & Airasian, 2003: p. 141) argue that “a valid test is always reliable but a reliable test is not always valid”. For this reason the reliability of the pre-test, post-test was established after the validity considerations, using the Spearman-Brown formula. For this purpose, the test was given
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to the pilot sample for testing. The pilot sample wrote the test twice within three weeks. The marks obtained (Appendix E) were used to calculate the Spearman correlation coefficient using SPSS. The marks yielded a Spearman correlation coefficient of 0.65. Appendix F shows a detailed table of the SPSS results of the calculation of the Spearman correlation coefficient. This was then used in the Spearman-Brown formula to determine the reliability of the test instrument. The Spearman-Brown formula yielded a reliability coefficient of 0.79. The interpretation of this coefficient of reliability follows from the fact that reliability is the degree to which a test consistently measures whatever it measures. Reliability is usually expressed numerically ranging from 0.0 to 1.0; so that a high coefficient indicates high reliability. Looking at the range 0.0 to 1.0 for estimating the coefficient of reliability, the reliability of 0.79 for the pre-test, post-test used in this research can be said to be established.
It is important that observation is as objective as possible. Therefore, observers must not bring into the observations, their own interests and biases. To measure the reliability of the observation schedule, three observation practice sessions were arranged by the researcher in the school used for piloting. In the three practice sessions, the researcher and a colleague Physical Science teacher, who is also a registered masters student at the Institute for Science and Technology Education (ISTE) at the University of South Africa (UNISA) observed the three lessons together but independently. The results were compared and checked for consistency and agreements at the end of each observation session. There was about 89% agreement on the statements in the schedule for the three practice sessions. After the three practice sessions the researcher used the observation schedule to observe lessons in the main research study. After each observation, field notes were written immediately to ensure that, memories of what was observed during the lesson was intact as much as possible.