More info on common lottery algorithm

[Anonymous]

Here is the part that I find misleading in the Q&A:

"The matching algorithm assigns each student a random lottery number and attempts to match each student with his or her first choice first, then his or her second choice, and so on. A student’s ranking of schools (the order a student puts schools on his or her application) is critical because the matching algorithm attempts to match each student with his or her first choice first, then his or her second choice, and so on.

I think a better way to say it is: "The computer assigns each student a single tracking number for the lottery. The lottery algorithm uses a complex formula to assign students to schools based on randomization of tracking numbers for each school within the preferences allowed for that school (in-boundary, sibling, proximity, founder, etc.)." I would stay away from saying that they try to assign you to your first choice, second choice, etc., because it leads people to believe that they choose you in the lottery and then the computer puts you in your highest-ranked choice that has a space, and that is not how it happens.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:It sounds like the FAQ is misleading, either in referring to a deferre acceptance algorithm or in repeatedly referring to a single "lottery number." If someone invoved in the process is reading this can they please change the FAQ so it is accurate and clear? Unlike some of the pps I do not "trust" an explanation posted anonymously on a message board by someone claiming to have insider knowledge.

Different poster, that's fine that you don't trust the other person, but you do understand that either way, nothing changes about what you should do in applying, right? That's the thing - we are all having a very nice conversation about how the algorithm works, but the most important issue is whether it working one way or another changes what we as parents do in the best interest of our kids. It doesn't change. Rank the schools in the order in which you most hope to attend.

So for that reason, sure, request they update the website, but really it won't change anything one way or another, so not sure I understand the big deal beyond us "algorithm nerds" who want to know every.single.detail.

+1. Nobody's getting extra credit for understanding the algorithm. It would be nice if all the official language that was distributed was a little clearer, and if some myschooldc people didn't give out bad information in the beginning, but the instructions for general users have always been crystal clear.

Agree, but I think the website needs to be as clear as possible on how this works. In the last thread there were people speculating about ways to do better in the lottery by listing your 12 schools stragecially (rather than in true preference order).

[Anonymous]

Anonymous wrote:Here is the part that I find misleading in the Q&A:

"The matching algorithm assigns each student a random lottery number and attempts to match each student with his or her first choice first, then his or her second choice, and so on. A student’s ranking of schools (the order a student puts schools on his or her application) is critical because the matching algorithm attempts to match each student with his or her first choice first, then his or her second choice, and so on.

I think a better way to say it is: "The computer assigns each student a single tracking number for the lottery. The lottery algorithm uses a complex formula to assign students to schools based on randomization of tracking numbers for each school within the preferences allowed for that school (in-boundary, sibling, proximity, founder, etc.)." I would stay away from saying that they try to assign you to your first choice, second choice, etc., because it leads people to believe that they choose you in the lottery and then the computer puts you in your highest-ranked choice that has a space, and that is not how it happens.

Email sent. We'll see!

[Anonymous]

Anonymous wrote:

Anonymous wrote:Here is the part that I find misleading in the Q&A:

"The matching algorithm assigns each student a random lottery number and attempts to match each student with his or her first choice first, then his or her second choice, and so on. A student’s ranking of schools (the order a student puts schools on his or her application) is critical because the matching algorithm attempts to match each student with his or her first choice first, then his or her second choice, and so on.

I think a better way to say it is: "The computer assigns each student a single tracking number for the lottery. The lottery algorithm uses a complex formula to assign students to schools based on randomization of tracking numbers for each school within the preferences allowed for that school (in-boundary, sibling, proximity, founder, etc.)." I would stay away from saying that they try to assign you to your first choice, second choice, etc., because it leads people to believe that they choose you in the lottery and then the computer puts you in your highest-ranked choice that has a space, and that is not how it happens.

Email sent. We'll see!

Thanks!

[Anonymous]

Anonymous wrote:

Anonymous wrote:It sounds like the FAQ is misleading, either in referring to a deferre acceptance algorithm or in repeatedly referring to a single "lottery number." If someone invoved in the process is reading this can they please change the FAQ so it is accurate and clear? Unlike some of the pps I do not "trust" an explanation posted anonymously on a message board by someone claiming to have insider knowledge.

I called the Deputy Mayor for Education's office and spoke with someone involved in the development of the lottery. They said they are use the Gale-Shapley deferred acceptance algorithm, without the trades in the New Orleans link above. PP is correct--the "lottery #" would better be called a "tracking number" as in last year's lottery. I would call the My School DC hotline or the DME office to confirm (and make sure they are telling everyone the same thing!).

I think that the FAQ is correct and the PP is incorrect. The Gale-Shapley algorithm says nothing about randomizing the results for each school. It can be done, but it is not a necessary feature. A good summary of Gale-Shapley, in mostly clear English, is here:

http://en.wikipedia.org/wiki/Stable_marriage_problem

[Anonymous]

Anonymous wrote:It sounds like the FAQ is misleading, either in referring to a deferre acceptance algorithm or in repeatedly referring to a single "lottery number." If someone invoved in the process is reading this can they please change the FAQ so it is accurate and clear? Unlike some of the pps I do not "trust" an explanation posted anonymously on a message board by someone claiming to have insider knowledge.

The FAQ is correct. There is a deferred acceptance algorithm and there is a single lottery number (which is not the same as the tracking number).

Deferred acceptance is required whenever the preference for all students is not the same at every school. If the preference is the same at every school, you just start with the highest-ranked lottery number, assign them to their top-ranked school, and go from there. However, if different students are ranked differently by different schools, you have to have deferred acceptance. There are two ways this can happen. One is if each school does its own drawing. That is not the way DC works. The other is if all schools use the same lottery number, but each school has its own preferences that supercede lottery numbers (in-boundary, sibling, proximity). Those preferences are school-specific, so your rank at various schools is different, even with the same lottery number. That is how DC works.

Another poster keeps talking about the trades that New Orleans does. Trades are not possible when using Gale-Shapley deferred acceptance. Gale-Shapley is a "stable" solution, by definition a stable solution one in which trades are impossible. From the wikipedia article:

"a matching is stable when there does not exist any alternative pairing (A, B) in which both A and B are individually better off than they would be with the element to which they are currently matched."


http://en.wikipedia.org/wiki/Stable_marriage_problem

[Anonymous]

Anonymous wrote:

Anonymous wrote:It sounds like the FAQ is misleading, either in referring to a deferre acceptance algorithm or in repeatedly referring to a single "lottery number." If someone invoved in the process is reading this can they please change the FAQ so it is accurate and clear? Unlike some of the pps I do not "trust" an explanation posted anonymously on a message board by someone claiming to have insider knowledge.

The FAQ is correct. There is a deferred acceptance algorithm and there is a single lottery number (which is not the same as the tracking number).

Deferred acceptance is required whenever the preference for all students is not the same at every school. If the preference is the same at every school, you just start with the highest-ranked lottery number, assign them to their top-ranked school, and go from there. However, if different students are ranked differently by different schools, you have to have deferred acceptance. There are two ways this can happen. One is if each school does its own drawing. That is not the way DC works. The other is if all schools use the same lottery number, but each school has its own preferences that supercede lottery numbers (in-boundary, sibling, proximity). Those preferences are school-specific, so your rank at various schools is different, even with the same lottery number. That is how DC works.

Another poster keeps talking about the trades that New Orleans does. Trades are not possible when using Gale-Shapley deferred acceptance. Gale-Shapley is a "stable" solution, by definition a stable solution one in which trades are impossible. From the wikipedia article:

"a matching is stable when there does not exist any alternative pairing (A, B) in which both A and B are individually better off than they would be with the element to which they are currently matched."


http://en.wikipedia.org/wiki/Stable_marriage_problem

This is incorrect, but as PPs note, it does not matter. Just rank the schools in your preference order, and be done with it!

[Anonymous]

Newbie here. This thread has been helpful. Thanks to all for the good info.

Do I have this right: we are IB for Hearst for PK. It seems like given past numbers we would likely get a spot. But I work near where Mundo Verde is moving and DH works near Ross. So if we put 1. Mundo Verde. 2. Ross. 3. Hearst and choose nothing else we likely would get wait list for 1 and 2 but get into Hearst? Do I have that right?

We would be happy with Hearst but Spanish immersion would be nice and proximity to DH work a bonus. Thanks.

[Anonymous]

Anonymous wrote:Newbie here. This thread has been helpful. Thanks to all for the good info.

Do I have this right: we are IB for Hearst for PK. It seems like given past numbers we would likely get a spot. But I work near where Mundo Verde is moving and DH works near Ross. So if we put 1. Mundo Verde. 2. Ross. 3. Hearst and choose nothing else we likely would get wait list for 1 and 2 but get into Hearst? Do I have that right?

We would be happy with Hearst but Spanish immersion would be nice and proximity to DH work a bonus. Thanks.

yes, that is correct. The only risk you raise is if you get into MV or Ross in rounds 1 or 2 the decision is made and you lose your Hearst spot.

[Anonymous]

Anonymous wrote:

Anonymous wrote:Newbie here. This thread has been helpful. Thanks to all for the good info.

Do I have this right: we are IB for Hearst for PK. It seems like given past numbers we would likely get a spot. But I work near where Mundo Verde is moving and DH works near Ross. So if we put 1. Mundo Verde. 2. Ross. 3. Hearst and choose nothing else we likely would get wait list for 1 and 2 but get into Hearst? Do I have that right?

We would be happy with Hearst but Spanish immersion would be nice and proximity to DH work a bonus. Thanks.

yes, that is correct. The only risk you raise is if you get into MV or Ross in rounds 1 or 2 the decision is made and you lose your Hearst spot.

Yeah, you should order them in your true preference. So if MV is really #1, then leave it there.
I don't think you have a shot at all at Ross, given how many IB students want in and can't get in before K, but it never hurts if you don't have anything else that you want. And I agree that based on past trends, you are likely to get into Hearst.

[Anonymous]

When a spot opens up in one of your higher (more preferred) ranked picksafter the first round, do you automatically get booted out of your current pick? How long do you have to decide whether to accept a spot off the waitlist? And would that be handled by myschooldc or by individual schools?

[Anonymous]

Anonymous wrote:When a spot opens up in one of your higher (more preferred) ranked picksafter the first round, do you automatically get booted out of your current pick? How long do you have to decide whether to accept a spot off the waitlist? And would that be handled by myschooldc or by individual schools?

I think it is handled by the individual schools, and you have to tell the school with which you have enrolled that you no longer want the spot. However, I talked to some of the school reps at the expo about it, and they said that there is going to be regular auditing to make sure that schools are gong in the correct order on the waitlist and to make sure that people are not holding two spots. I don't know if there are uniform timeframes for making a decision about a spot--I would think that would be up to the school.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:Newbie here. This thread has been helpful. Thanks to all for the good info.

Do I have this right: we are IB for Hearst for PK. It seems like given past numbers we would likely get a spot. But I work near where Mundo Verde is moving and DH works near Ross. So if we put 1. Mundo Verde. 2. Ross. 3. Hearst and choose nothing else we likely would get wait list for 1 and 2 but get into Hearst? Do I have that right?

We would be happy with Hearst but Spanish immersion would be nice and proximity to DH work a bonus. Thanks.

yes, that is correct. The only risk you raise is if you get into MV or Ross in rounds 1 or 2 the decision is made and you lose your Hearst spot.

Yeah, you should order them in your true preference. So if MV is really #1, then leave it there.
I don't think you have a shot at all at Ross, given how many IB students want in and can't get in before K, but it never hurts if you don't have anything else that you want. And I agree that based on past trends, you are likely to get into Hearst.

We know an OOB family that got into PK4 at Ross off the waiting list (after school had already started). But it does happen, so it's not completely impossible... maybe just highly highly unlikely.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:Newbie here. This thread has been helpful. Thanks to all for the good info.

Do I have this right: we are IB for Hearst for PK. It seems like given past numbers we would likely get a spot. But I work near where Mundo Verde is moving and DH works near Ross. So if we put 1. Mundo Verde. 2. Ross. 3. Hearst and choose nothing else we likely would get wait list for 1 and 2 but get into Hearst? Do I have that right?

We would be happy with Hearst but Spanish immersion would be nice and proximity to DH work a bonus. Thanks.

yes, that is correct. The only risk you raise is if you get into MV or Ross in rounds 1 or 2 the decision is made and you lose your Hearst spot.

Yeah, you should order them in your true preference. So if MV is really #1, then leave it there.
I don't think you have a shot at all at Ross, given how many IB students want in and can't get in before K, but it never hurts if you don't have anything else that you want. And I agree that based on past trends, you are likely to get into Hearst.

We know an OOB family that got into PK4 at Ross off the waiting list (after school had already started). But it does happen, so it's not completely impossible... maybe just highly highly unlikely.

And OP should def apply there if she is interested and only has 3 schools total. I would say not worth it if you had filled up all your slots with other schools, but def worth it if you haven't.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:Newbie here. This thread has been helpful. Thanks to all for the good info.

Do I have this right: we are IB for Hearst for PK. It seems like given past numbers we would likely get a spot. But I work near where Mundo Verde is moving and DH works near Ross. So if we put 1. Mundo Verde. 2. Ross. 3. Hearst and choose nothing else we likely would get wait list for 1 and 2 but get into Hearst? Do I have that right?

We would be happy with Hearst but Spanish immersion would be nice and proximity to DH work a bonus. Thanks.

yes, that is correct. The only risk you raise is if you get into MV or Ross in rounds 1 or 2 the decision is made and you lose your Hearst spot.

Yeah, you should order them in your true preference. So if MV is really #1, then leave it there.
I don't think you have a shot at all at Ross, given how many IB students want in and can't get in before K, but it never hurts if you don't have anything else that you want. And I agree that based on past trends, you are likely to get into Hearst.

Wait, why does the number of slots matter? If you rank Ross #1, you stay on their waitlist, period, end of story. If you get into your #7 or #3, you still stay on Ross's waitlist. Why would picking 2 other schools, vs picking 12 schools total, affect your chances at Ross at all?
We know an OOB family that got into PK4 at Ross off the waiting list (after school had already started). But it does happen, so it's not completely impossible... maybe just highly highly unlikely.

And OP should def apply there if she is interested and only has 3 schools total. I would say not worth it if you had filled up all your slots with other schools, but def worth it if you haven't.