Z score, scores more than marks!
- වික්රමභාහු කරුණාරත්න O ne professor, defending the government argued “The Z scores calculated for the three subjects of each student i...
http://weadikawa.blogspot.com/2012/01/z-score-scores-more-than-marks.html
- වික්රමභාහු කරුණාරත්න
One professor, defending the government argued “The Z scores calculated for the three subjects of each student is averaged and a composite Z score of each student is calculated. There was absolutely no debacle with results up to this point and everything was in order. Then the composite Z score of the students needed to be arranged from the highest to the lowest value to provide the corresponding all island merit rank. The dilemma arose here, on the approach to be adopted, in preparing a single series of data for national ranking from two different examinations held for old and new syllabus. It is obvious even for a layman to understand that marks of two different examinations conducted for two different groups of candidates under two different syllabus cannot be pooled directly even though the marks are brought down to a standard normal distribution using Z scores.” Yes, all these were obvious to many of us. It is not difficult to understand that performance of a student in one subject cannot be estimated with the performance of another subject which has different subjective examination conditions by comparing raw marks. This is exactly why Z scores are calculated and used in comparing performance of different subjects. But why should a dilemma arise for different examinations held for old and new syllabus. If exam papers are different and syllabuses are different then these are like two subjects. How come this became a special problem this year? Did we not face this problem from the inception of Z score evaluation?
Lack of forward planning
One professor, defending the government argued “The Z scores calculated for the three subjects of each student is averaged and a composite Z score of each student is calculated. There was absolutely no debacle with results up to this point and everything was in order. Then the composite Z score of the students needed to be arranged from the highest to the lowest value to provide the corresponding all island merit rank. The dilemma arose here, on the approach to be adopted, in preparing a single series of data for national ranking from two different examinations held for old and new syllabus. It is obvious even for a layman to understand that marks of two different examinations conducted for two different groups of candidates under two different syllabus cannot be pooled directly even though the marks are brought down to a standard normal distribution using Z scores.” Yes, all these were obvious to many of us. It is not difficult to understand that performance of a student in one subject cannot be estimated with the performance of another subject which has different subjective examination conditions by comparing raw marks. This is exactly why Z scores are calculated and used in comparing performance of different subjects. But why should a dilemma arise for different examinations held for old and new syllabus. If exam papers are different and syllabuses are different then these are like two subjects. How come this became a special problem this year? Did we not face this problem from the inception of Z score evaluation?
Lack of forward planning
Then the good professor goes on to say “The criticism raised here for the delay in realizing the issue of two different examinations held separately is fair and examination authorities are responsible for the lack of forward planning. The discussions took place between Examination Department and University Grants Commission in transferring the responsibility of proposing a suitable approach in amalgamating Z scores of two examinations.” This was the beginning of the great mess up. Instead of using the method used in the previous years, every body including these so called professors, wanted 
to obey the dictates from the president. The application deadlines for foreign universities were approaching and the students and parents were anxious on the issue. The President instructed to convene a meeting with relevant officials both from Examination Department and UGC and advised to release the results without further delay. The expert committee worked out a formula to combine the Z scores of the two examinations. This is absurd. If Z score can be amalgamated without a flaw why not amalgamate for all subjects? Or much easier why not go back to raw marks and add the arithmetical total as we used to do in the past. Professor Ralph Thattil who introduced the Z score to Lanka said that the formula used to tally the Z score of students who sat from two different syllabus is wrong.
LAKBIMAnEWS reported that The Presidential Committee appointed to investigate the GCE A/L results fiasco did not look into the charges that the Z-Score formula used was wrong because it was not within their mandate. Head of the committee, Dhara Wijethilaka has added that they were not mandated to investigate the Z-score and did not interview Prof. Thattil. She explained “We were clearly told to look at the errors which occurred over the District Rankings. We did not interview the professor because we were not investigating the Z-Score formula.” All are now aware that the mistake is made in calculating the Z score. In spite of the fact that both the present education minister and the previous education ministers have washed their hands off from this discussion simply claiming ignorance, it remains a burning question among those who value education. Every body could see that this mess up is an attack on free education. All must get together to force the government to go for an overall re-correction free of charge. Firstly all answer scripts should be checked for proper raw marks, secondly Z score should be calculated without amalgamation, and final results should be given as we used to do in the past as explained by professor Thattil and others. Remember we are not fighting for Z score but for the continuation of free education.
to obey the dictates from the president. The application deadlines for foreign universities were approaching and the students and parents were anxious on the issue. The President instructed to convene a meeting with relevant officials both from Examination Department and UGC and advised to release the results without further delay. The expert committee worked out a formula to combine the Z scores of the two examinations. This is absurd. If Z score can be amalgamated without a flaw why not amalgamate for all subjects? Or much easier why not go back to raw marks and add the arithmetical total as we used to do in the past. Professor Ralph Thattil who introduced the Z score to Lanka said that the formula used to tally the Z score of students who sat from two different syllabus is wrong.LAKBIMAnEWS reported that The Presidential Committee appointed to investigate the GCE A/L results fiasco did not look into the charges that the Z-Score formula used was wrong because it was not within their mandate. Head of the committee, Dhara Wijethilaka has added that they were not mandated to investigate the Z-score and did not interview Prof. Thattil. She explained “We were clearly told to look at the errors which occurred over the District Rankings. We did not interview the professor because we were not investigating the Z-Score formula.” All are now aware that the mistake is made in calculating the Z score. In spite of the fact that both the present education minister and the previous education ministers have washed their hands off from this discussion simply claiming ignorance, it remains a burning question among those who value education. Every body could see that this mess up is an attack on free education. All must get together to force the government to go for an overall re-correction free of charge. Firstly all answer scripts should be checked for proper raw marks, secondly Z score should be calculated without amalgamation, and final results should be given as we used to do in the past as explained by professor Thattil and others. Remember we are not fighting for Z score but for the continuation of free education.
වික්රමභාහු කරුණාරත්න
උපුටා ගැනීම
2012-01-22
