දෙබිඩි බටහිර ජඩමාධ්‍ය හා දෙමළ ජාතිවාදය

             සිංහල ලිත් ඉලක්කම්

දෙබිඩි බටහිර ජඩමාධ්‍ය හා දෙමළ ජාතිවාදය

බටහිරයන්ගේ  අවශ්‍යතාවට, පැරදවිය නොහැකි බවට රොහාන් ගුණරත්න වැනි ඊනියා යුද විශේෂඥයන් විසින් ප්‍රකාශ කෙරුණ ද ප්‍රභාකරන් හා ඔහුගේ ත්‍රස්තවාදී කණ්ඩායම 2019 මැයි 19 වැනි දා නන්දිකඩාල් හි පරාජය කෙරුණා. එය ඊනියා යුද විශේෂඥයන් හා බටහිරයන් ලැබූ පරාජයක්. එහෙත් අපට බටහිර මාධ්‍ය විසින් ගෙන යනු ලැබූ ප්‍රචාරය පරාජය කරන්න බැරි වුණා. තවමත් ඒ ප්‍රචාරක යුද්ධය කෙරී ගෙන යනවා.

Z score and the concerned parent

I refer to the piece by a "concerned parent" on ‘The Z-Score and Professorial Pronouncements’ published in the Sunday Island on 12th February 2012. He is surprised that I did not consult Natha Deviyo on the Z score and tells the readers that, unlike the other Professors mentioned by him, Prof. Carlo Fonseka and I "have tended to obfuscate the issue and create confusion in the minds of the reader". I respect Prof. Fonseka more than most of the other Professors in Sri Lanka, though I have differences in opinion with him when it comes to Epistemology, the so called ethnic problem and Marxism, and I do not think he tended to obfuscate the issue and create confusion in the minds of the reader. Neither did I and as far as I am concerned I only tried to point out number of factors that both Prof. Thatil and others, and the members of the panel of experts appointed to propose a scheme of standardization had not considered. It has to be pointed out the panel of experts consisted of western Statisticians, I suppose of the same calibre as Prof. Thatil.

One of the factors I mentioned was the difference in the populations that sat for the examination in any subject in the old syllabus and the new syllabus. In any normal year the students who sit for the first time and the repeaters sit the same paper and are "pooled" in determining the Z score in any subject. This year as well as in 2001, in each subject there were two groups, one sitting for the first time and the other consisting of repeaters. The scheme that Prof. Thatil had introduced looks after the degree in difficulty with respect to different subjects and not with respect to the differences in the "merits" of the group of repeaters and the others in any subject. I believe that it is in order to look after this problem that pooling has been suggested by the panel of experts. I have no problem with pooling in principle, but I found that the "formula" that they had adopted was not quite correct. Having said that I mentioned that the differences in difficulty also had to be looked after and suggested after pooling and scaling, the students should be regrouped or "de-pooled" and another standardization should be carried out along the lines introduced by Prof. Thatil. It is not a recommendation as such and I am of the opinion pooling is more important than Thatil standardization.

In the articles I have read many had expressed the idea that populations of the two groups who sat for the first time and those who repeated cannot be pooled without giving any reason whatsoever as to why they cannot be pooled. In a normal year these groups are "pooled" or considered together and one has to come out with a convincing reason as to why they cannot be pooled without merely stating that populations cannot be pooled. I tend to think that in 2001 all the experts did not either consider the differences due to "merit" in the groups of repeaters and first timers or have a solution to the problem.

I did not consult Natha Deviyo in this case for the reason that I know that Natha Deviyo would not answer such questions, among others. Natha Deviyo is more concerned with people dying (two people per day) of Rajarata Kidney Disease and already he had given instructions on the cause of the disease, as western medicine has no answer to the problem. On the other hand there are western statistical methods to deal with standardization, a concept arising in the west, and I know that people are interested in solving this particular problem within the method of standardization, without waiting for us to come out with our own solutions. With respect to solving these problems in the courts of law I was reiterating a statement by Feyerabend on so called expert opinion in Science, with which I agree. It may be the accepted way of solving the problems, meaning the way imposed on us by the westerners how to solve such problems, but according to the traditions of my culture I question the so called accepted methods whether in law statistics or science, especially since we would not be independent unless we are independent of the knowledge of the westerners dominating our thinking, if we are thinking at all.

Copyright Prof. Nalin De Silva

Z Score then and now

It is very often said that when Z score scaling process was introduced in 2001 there was no problem and the Supreme Court agreed with the scheme proposed by the Educational Authorities but now a problem has arisen due to the pooling of populations advocated by a panel of “experts” in Statistics. In 2001 Z scores of individual candidates were added and then taken the mean dividing by four or three depending on the number of subjects that the candidate had sat.

As has been mentioned previously Z scores in different subjects can be compared but that does not make them equivalent and a Z score of x in a subject A is not equivalent to the same Z score of x in subject B. Nevertheless the University admissions are based on Z score and we will stick to the Z score scaling process for the time being.

Scaling of marks is usually done when the populations are different. The differences in populations could arise due to various reasons. The students sitting for two different subjects belong to two different populations and similarly students sitting for either the old syllabus or the new syllabus in the same subject have to be considered as belonging to two different populations.

Under normal circumstances (say from 2004 to 2010) when in each year the subjects were the same and the syllabi had not been changed the differences in the populations arose mainly as a result of degree of hardness of the question papers in each subject, though strictly speaking the degree of hardness in each paper of the same subject also had to be taken into account, assuming of course that there was no difference between say the quality of the students sitting the examination in different subjects. In such years assuming that the Z scores are equivalent the individual Z scores of a candidate in each subject may be added and then the mean can be calculated for the purpose of ranking of students.

However, when the syllabi are changed there is another difference in the populations that has to be taken into consideration. It is due to the fact that in each subject there are two different populations sitting the examination, one in the new syllabus and the other in the old syllabus. The first group consists of students sitting for the first time and the second group sitting for the second or the third time. The quality of the students of the two groups is not the same and some remedial scaling process has to be adopted when such situations arise. The “expert” panel has come out with a procedure called pooling and they have suggested a formula to be adopted. It is not a formula of the UGC or the Examinations Department or the Ministries of Education and Higher Education but one that has been proposed by a panel of “experts” in Statistics. I myself have a difference of opinion on the formula though I am not an “expert” in Statistics by any stretch of imagination, but in principle I agree with the suggestion of a formula for pooling by the panel.

As has been suggested already, marks can be pooled and scaled first and then such scaled marks can be rescaled after de-pooling or regrouping, using the Z scores, if it is Statistically sound, thus taking into consideration both the differences in populations due to the quality of students and due to the degree of hardness of the subjects. In 2001, 2002 and 2003, as I understand, there was no way of first pooling and scaling taking into consideration the differences in quality of students as not only the number of subjects had been reduced from four to three but in certain cases subjects such as Pure Mathematics, Applied Mathematics, Botany and Zoology had been dropped altogether adding new subjects such as Combined Mathematics and Biology. In 2011 (and in 2012 and 2013) the subjects remain the same though the syllabi have been changed.

Nalin De Silva

Z Score then and now

It is very often said that when Z score scaling process was introduced in 2001 there was no problem and the Supreme Court agreed with the scheme proposed by the Educational Authorities but now a problem has arisen due to the pooling of populations advocated by a panel of “experts” in Statistics. In 2001 Z scores of individual candidates were added and then taken the mean dividing by four or three depending on the number of subjects that the candidate had sat.

As has been mentioned previously Z scores in different subjects can be compared but that does not make them equivalent and a Z score of x in a subject A is not equivalent to the same Z score of x in subject B. Nevertheless the University admissions are based on Z score and we will stick to the Z score scaling process for the time being.

Scaling of marks is usually done when the populations are different. The differences in populations could arise due to various reasons. The students sitting for two different subjects belong to two different populations and similarly students sitting for either the old syllabus or the new syllabus in the same subject have to be considered as belonging to two different populations.

Under normal circumstances (say from 2004 to 2010) when in each year the subjects were the same and the syllabi had not been changed the differences in the populations arose mainly as a result of degree of hardness of the question papers in each subject, though strictly speaking the degree of hardness in each paper of the same subject also had to be taken into account, assuming of course that there was no difference between say the quality of the students sitting the examination in different subjects. In such years assuming that the Z scores are equivalent the individual Z scores of a candidate in each subject may be added and then the mean can be calculated for the purpose of ranking of students.

However, when the syllabi are changed there is another difference in the populations that has to be taken into consideration. It is due to the fact that in each subject there are two different populations sitting the examination, one in the new syllabus and the other in the old syllabus. The first group consists of students sitting for the first time and the second group sitting for the second or the third time. The quality of the students of the two groups is not the same and some remedial scaling process has to be adopted when such situations arise. The “expert” panel has come out with a procedure called pooling and they have suggested a formula to be adopted. It is not a formula of the UGC or the Examinations Department or the Ministries of Education and Higher Education but one that has been proposed by a panel of “experts” in Statistics. I myself have a difference of opinion on the formula though I am not an “expert” in Statistics by any stretch of imagination, but in principle I agree with the suggestion of a formula for pooling by the panel.

As has been suggested already, marks can be pooled and scaled first and then such scaled marks can be rescaled after de-pooling or regrouping, using the Z scores, if it is Statistically sound, thus taking into consideration both the differences in populations due to the quality of students and due to the degree of hardness of the subjects. In 2001, 2002 and 2003, as I understand, there was no way of first pooling and scaling taking into consideration the differences in quality of students as not only the number of subjects had been reduced from four to three but in certain cases subjects such as Pure Mathematics, Applied Mathematics, Botany and Zoology had been dropped altogether adding new subjects such as Combined Mathematics and Biology. In 2011 (and in 2012 and 2013) the subjects remain the same though the syllabi have been changed.

Copyright Prof. Nalin De Silva