2011 PSLE Discussions and Strategy

[jtoh]

2ppaamm:

linden2000:

http://www.facebook.com/notes/ministry-of-education-singapore/measures-in-place-in-exam-and-admissions-systems-to-relieve-pressure-on-students/10150302450237004


This note seems to suggest grades are not bell curve-fitted or am I interpreting it wrongly?

I think that article came after a lot of talk about PSLE being on the curve and the problems it presents. Specifically it is clear that there is no quota to the number of A* or As in any subject, this means that MOE does not determine the number of A*s and As based on the bell curve. If a student gets >91, he gets an A*. It means A* (or any grade) is based upon the absolute score of the child and not in comparison to the cohort. That's clear.

What's not mentioned is the way the T-score is calculated. For each subject, the T-score = 50+10*[(x-mean)/s.d.]

Compare that to the bell curve or normdist calculation of z-value, z=(x-mean)/s.d.

In our PSLE T-score, they multiple that z value by 10 and then add 50 to it. These are constants and therefore, no matter how you plot it, it will be a bell-curve. Hence, the subject subject T-score is a PERFECT bell curve.

The T-score for the 4 subjects are then added for each child for the PSLE T-score. Hence, while the PSLE T-score may not be a perfect bell curve, it is an aggregation of 4 (or 3) bell curves.

Hope I make sense?

If you follow me so far, it would mean that if the exam paper is easy that year, the mean will be very high, and assuming the s.d. is constant from year to year, your child's T-score will still be around the same, but the number of A* and A will increase. The reverse is true for difficult papers.

Now if you are still with me, if you have a very diverse group of student that year, then the s.d. could be very high, and we hold the difficulty of the paper constant, the range of the PSLE T-score in the cohort is large compared to a cohort with more uniform performers.

Now, we have the PSLE T-score cracked. Hopefully those who have more insights can shed more light. I am looking at it at a pure mathematical/statistical view. Which should apply.

Hi Pam,

Thanks for the explanation. I think I understand it.

A question. If as MOE says, the number of A/A* is not pre-determined and that a score of >91 secures you an A* and >70 an A, why is it from year to year, regardless of whether the paper is difficult or easy, the number of A/A* for Math/English/Science usually hovers around 40% and CL usually around 80%? Or is it the case that in a year of difficult Math paper, there are many more As than A* but the statistics do not reveal this as there's no breakdown into A and A*?

[2ppaamm]

jtoh:

2ppaamm:

[quote=\"linden2000\"]http://www.facebook.com/notes/ministry-of-education-singapore/measures-in-place-in-exam-and-admissions-systems-to-relieve-pressure-on-students/10150302450237004


This note seems to suggest grades are not bell curve-fitted or am I interpreting it wrongly?

I think that article came after a lot of talk about PSLE being on the curve and the problems it presents. Specifically it is clear that there is no quota to the number of A* or As in any subject, this means that MOE does not determine the number of A*s and As based on the bell curve. If a student gets >91, he gets an A*. It means A* (or any grade) is based upon the absolute score of the child and not in comparison to the cohort. That's clear.

What's not mentioned is the way the T-score is calculated. For each subject, the T-score = 50+10*[(x-mean)/s.d.]

Compare that to the bell curve or normdist calculation of z-value, z=(x-mean)/s.d.

In our PSLE T-score, they multiple that z value by 10 and then add 50 to it. These are constants and therefore, no matter how you plot it, it will be a bell-curve. Hence, the subject subject T-score is a PERFECT bell curve.

The T-score for the 4 subjects are then added for each child for the PSLE T-score. Hence, while the PSLE T-score may not be a perfect bell curve, it is an aggregation of 4 (or 3) bell curves.

Hope I make sense?

If you follow me so far, it would mean that if the exam paper is easy that year, the mean will be very high, and assuming the s.d. is constant from year to year, your child's T-score will still be around the same, but the number of A* and A will increase. The reverse is true for difficult papers.

Now if you are still with me, if you have a very diverse group of student that year, then the s.d. could be very high, and we hold the difficulty of the paper constant, the range of the PSLE T-score in the cohort is large compared to a cohort with more uniform performers.

Now, we have the PSLE T-score cracked. Hopefully those who have more insights can shed more light. I am looking at it at a pure mathematical/statistical view. Which should apply.

Hi Pam,

Thanks for the explanation. I think I understand it.

A question. If as MOE says, the number of A/A* is not pre-determined and that a score of >91 secures you an A* and >70 an A, why is it from year to year, regardless of whether the paper is difficult or easy, the number of A/A* for Math/English/Science usually hovers around 40% and CL usually around 80%? Or is it the case that in a year of difficult Math paper, there are many more As than A* but the statistics do not reveal this as there's no breakdown into A and A*?[/quote]Not sure about that 40% and 80% thingy. I added a caveat.

[jtoh]

No problem Pam.

[linden2000]

2ppaamm:

linden2000:

http://www.facebook.com/notes/ministry-of-education-singapore/measures-in-place-in-exam-and-admissions-systems-to-relieve-pressure-on-students/10150302450237004


This note seems to suggest grades are not bell curve-fitted or am I interpreting it wrongly?

I think that article came after a lot of talk about PSLE being on the curve and the problems it presents. Specifically it is clear that there is no quota to the number of A* or As in any subject, this means that MOE does not determine the number of A*s and As based on the bell curve. If a student gets >91, he gets an A*. It means A* (or any grade) is based upon the absolute score of the child and not in comparison to the cohort. That's clear.

What's not mentioned is the way the T-score is calculated. For each subject, the T-score = 50+10*[(x-mean)/s.d.]

Compare that to the bell curve or normdist calculation of z-value, z=(x-mean)/s.d.

In our PSLE T-score, they multiple that z value by 10 and then add 50 to it. These are constants and therefore, no matter how you plot it, it will be a bell-curve. Hence, the subject subject T-score is a PERFECT bell curve.

The T-score for the 4 subjects are then added for each child for the PSLE T-score. Hence, while the PSLE T-score may not be a perfect bell curve, it is an aggregation of 4 (or 3) bell curves.

Hope I make sense?

If you follow me so far, it would mean that if the exam paper is easy that year, the mean will be very high, and assuming the s.d. is constant from year to year, your child's T-score will still be around the same, but the number of A* and A will increase. The reverse is true for difficult papers.

Now if you are still with me, if you have a very diverse group of student that year, then the s.d. could be very high, and we hold the difficulty of the paper constant, the range of the PSLE T-score in the cohort is large compared to a cohort with more uniform performers.

Now, we have the PSLE T-score cracked. Hopefully those who have more insights can shed more light. I am looking at it at a pure mathematical/statistical view. Which should apply.

And then a caveat. The PSLE is conducted by MOE only and no external or independent party is involved in its audit. Hence, MOE can manipulate it in anyway it wants/deems fit. It is answerable to nobody on how each child's T-score is calculated. This is a Singapore only exam, and therefore nobody else in the world uses its mechanism, or recognize its purpose. So PSLE is purposeless outside Singapore and even in Singapore, is used as a placement exam only at secondary school level.

So, if the T-score deviates, nobody can understand why or audit the process. It will be a mystery. :scratchhead: Hope this helps!

Thanks for the clarification.
Generally easy paper means higher number of A and A* since these are not bell-curve fitted. But not necessarily higher t-scores because of higher mean (since T-scores are calculated relative to the cohort).

[2ppaamm]

linden2000:

Thanks for the clarification.
Generally easy paper means higher number of A and A* since these are not bell-curve fitted. But not necessarily higher t-scores because of higher mean (since T-scores are calculated relative to the cohort).

Yes, that's about it.

[less kiasu liao]

Hi, everyone, long time follower but newbie poster of this forum. Thank you all for your company all this while.:-)


Thanks ngbrdad for raising my dd’s case of unexpectedly scoring A for CL but distinction for HCL. Some of her usual top EL scorers in her school also scored only A in the PSLE (hers was A* still) but their marks remained in the 260s. Noticed that among the 250s, no one scored A* for CL.

Incidentally, I heard from a friend that SEAB’s directive was to be lenient in EL this year.

Cedar’s principal indicated during open house that the number of IP was not fixed, so I wonder if MOE will fix a cut off point instead. Guess that will be anywhere between mid 250s to 258. Anyone can give a closer gauge?

Lastly, hope all our kids get into schools that are good for them, though not necessary the bland name ones… From my family’s experience, that is all that matters in the end.

[jhjkksdad]

linden2000:

http://www.facebook.com/notes/ministry-of-education-singapore/measures-in-place-in-exam-and-admissions-systems-to-relieve-pressure-on-students/10150302450237004


This note seems to suggest grades are not bell curve-fitted or am I interpreting it wrongly?

Yes, and MOE statistics seems to indicate so as well.

However, I notice that MOE always publish statistics as 'A and A*', even in the above referenced link, but not A* alone. My take is that there is no quota for the category 'A' alone and as such no quota for 'A and A*', but category 'A*' alone would be curve fitted.

Reason being I doubt it is easy to get above 90 for languages and science. I believe my son's languages are good but yet he has almost never scored above 90 since P4 save I think once. And very few do in his class which is an A class. Yet many more of them got A* in PSLE.

[Augmum]

linden2000:

http://www.facebook.com/notes/ministry-of-education-singapore/measures-in-place-in-exam-and-admissions-systems-to-relieve-pressure-on-students/10150302450237004


This note seems to suggest grades are not bell curve-fitted or am I interpreting it wrongly?

so is it means that these teachers had provided us, parents, the wrong info ??

apparently, in my gal's pri sch, the Best in Eng pupil could not hit 91 or above.
when i raised my concern to her teacher, how could it possibly be.....
that the whole level, no 1 pupil could obtain an A* for Eng?? :scratchhead:
i was told that it would be a diff story in PSLE,
and she even gave me some figures for grade of A*.
eventually, their psle results revealed quite a number of them scoring A*.......

in addition, i heard fr a mummy whose child was in another sch, teacher telling her the same thing......
btw, this topic was in discussion b4 in this ksp forum,
there were some parents indicated that they heard the same explanation fr their children's teachers.....
really :roll: :boogie:

[Augmum]

jhjkksdad:

Reason being I doubt it is easy to get above 90 for languages and science. I believe my son's languages are good but yet he has almost never scored above 90 since P4 save I think once. And very few do in his class which is an A class. Yet many more of them got A* in PSLE.

:hi5:
this is what happened to my gal's sch...which made me to clarify fr her teacher.....

[jtoh]

But if MOE has come out to state it in writing, it should be the correct version? It wouldn’t be the first time that teachers have the wrong information.