Common Lottery Algorithm

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:
Child #1 has sibling preference but ranked school ABC at #3, and didn't get into their #1-2.
Child #2 has no preferences but ranked school ABC at #1.

Who gets the seat at school ABC?

What if child #2's lottery number is higher than child #1's?

Child #1. Sibling preference trumps no preference every time.

I second this. 100% according to the logic of stable match. School ABC prefers Child #2 over #1 so this creates an equitable match for all parties involved.

We were arguing this point yesterday, but as of yesterday, who is disputing this part of it?

The part we are now disputing is this:
Same scenario as above EXCEPT Child #2 DOES have sibling preference. Who gets the spot then if both children have sibling preference but Child #1 ranked the school #3 and didn't get into 1-2, vs. Child #2 who ranked the school #1?

If you believe parent ranking has no effect beyond what order the computer tries to place you, you believe basically that at this point it's random. Those of us saying parent ranking matters are saying that in THIS scenario, Child #2 will get the spot. Hands down. And random computer assigned lottery number does not impact anything at this point.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:
Child #1 has sibling preference but ranked school ABC at #3, and didn't get into their #1-2.
Child #2 has no preferences but ranked school ABC at #1.

Who gets the seat at school ABC?

What if child #2's lottery number is higher than child #1's?

Child #1. Sibling preference trumps no preference every time.

I second this. 100% according to the logic of stable match. School ABC prefers Child #2 over #1 so this creates an equitable match for all parties involved.

We were arguing this point yesterday, but as of yesterday, who is disputing this part of it?

The part we are now disputing is this:
Same scenario as above EXCEPT Child #2 DOES have sibling preference. Who gets the spot then if both children have sibling preference but Child #1 ranked the school #3 and didn't get into 1-2, vs. Child #2 who ranked the school #1?

If you believe parent ranking has no effect beyond what order the computer tries to place you, you believe basically that at this point it's random. Those of us saying parent ranking matters are saying that in THIS scenario, Child #2 will get the spot. Hands down. And random computer assigned lottery number does not impact anything at this point.

If there is a tie, then there is a tiebreaker and it is not based on parent rank. It's based on your randomly assigned lottery number according to the method documents found earlier in this thread.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:
Child #1 has sibling preference but ranked school ABC at #3, and didn't get into their #1-2.
Child #2 has no preferences but ranked school ABC at #1.

Who gets the seat at school ABC?

What if child #2's lottery number is higher than child #1's?

Child #1. Sibling preference trumps no preference every time.

I second this. 100% according to the logic of stable match. School ABC prefers Child #2 over #1 so this creates an equitable match for all parties involved.

We were arguing this point yesterday, but as of yesterday, who is disputing this part of it?

The part we are now disputing is this:
Same scenario as above EXCEPT Child #2 DOES have sibling preference. Who gets the spot then if both children have sibling preference but Child #1 ranked the school #3 and didn't get into 1-2, vs. Child #2 who ranked the school #1?

If you believe parent ranking has no effect beyond what order the computer tries to place you, you believe basically that at this point it's random. Those of us saying parent ranking matters are saying that in THIS scenario, Child #2 will get the spot. Hands down. And random computer assigned lottery number does not impact anything at this point.

So again, another parent who thinks that parent rank does something it doesn't. This isn't a different point at all, it's the point people have been shooting down for 48 hours.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

That is obvious. No one in any of these threads is disputing this.

Are you reading the same thread? People are questioning this on every page. People are stating that the parent ranking hold the more weight then it actually does. Go back to each page and you'll find at least one post where someone is saying having a school ranked #1 gives you priority over someone who ranked it #2 but with a better preference. That is not at all true and misrepresents a stable matching algorithm.

You conveniently cut out your post that I was responding to. Wow, are you that desperate to appear right?

Since you seem to have forgotten what you said:

Anonymous wrote:

Here's what putting a school at #1 does - it makes it your #1 school choice. If you get accepted in it, then great. If you don't then it moves down the line. It says, "I prefer this over the other schools I selected, so if I get in, I want to keep it". Your #2 school says "I prefer this over the other schools I selected accept for #1, and if I get into #2 then great! If I get into #1 then disregard #2 and give me #1".

You do not raise the bigger question that we are all arguing about in this quote. That is why THIS is obvious.

So, show ANYWHERE in this thread where the part of the process that you describe above is questioned?

4 posts above this (from 11:49) provide an example from page 14 where someone gets it wrong and assume a parent who ranks a school as #1 has greater weight than a parent who ranks the same school as #4.

Great, at least we're in agreement about this: no one is questioning what you said in the quotes. Because even the example you give here is not the same as what's in the quotes. Or do you not even understand what you yourself wrote?

[Anonymous]

The school rankings made by other parents/student have absolutely no affect on your capability of accepting a seat in the lottery. The only thing has an affect on your acceptance is as follows:

1) Someone with a better preference requests the same seat
2) You get accepted at a higher ranked school.

That's it. It doesn't matter what the rank of the school was in scenario #1. The algorithm ignores it. It's entirely possible that the kid accepted in scenario #1 moves on to another school (that he ranked higher) and you can get the seat back! That's how the algorithm works!

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:
Child #1 has sibling preference but ranked school ABC at #3, and didn't get into their #1-2.
Child #2 has no preferences but ranked school ABC at #1.

Who gets the seat at school ABC?

What if child #2's lottery number is higher than child #1's?

Child #1. Sibling preference trumps no preference every time.

I second this. 100% according to the logic of stable match. School ABC prefers Child #2 over #1 so this creates an equitable match for all parties involved.

We were arguing this point yesterday, but as of yesterday, who is disputing this part of it?

The part we are now disputing is this:
Same scenario as above EXCEPT Child #2 DOES have sibling preference. Who gets the spot then if both children have sibling preference but Child #1 ranked the school #3 and didn't get into 1-2, vs. Child #2 who ranked the school #1?

If you believe parent ranking has no effect beyond what order the computer tries to place you, you believe basically that at this point it's random. Those of us saying parent ranking matters are saying that in THIS scenario, Child #2 will get the spot. Hands down. And random computer assigned lottery number does not impact anything at this point.

If there is a tie, then there is a tiebreaker and it is not based on parent rank. It's based on your randomly assigned lottery number according to the method documents found earlier in this thread.

Source? What is your source that this is the way this lottery will work in this specific situation?

[Anonymous]

Anonymous wrote:The school rankings made by other parents/student have absolutely no affect on your capability of accepting a seat in the lottery. The only thing has an affect on your acceptance is as follows:

1) Someone with a better preference requests the same seat
2) You get accepted at a higher ranked school.

That's it. It doesn't matter what the rank of the school was in scenario #1. The algorithm ignores it. It's entirely possible that the kid accepted in scenario #1 moves on to another school (that he ranked higher) and you can get the seat back! That's how the algorithm works!

Source? What is your source that in this specific situation it works this way?

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:
Child #1 has sibling preference but ranked school ABC at #3, and didn't get into their #1-2.
Child #2 has no preferences but ranked school ABC at #1.

Who gets the seat at school ABC?

What if child #2's lottery number is higher than child #1's?

Child #1. Sibling preference trumps no preference every time.

I second this. 100% according to the logic of stable match. School ABC prefers Child #2 over #1 so this creates an equitable match for all parties involved.

We were arguing this point yesterday, but as of yesterday, who is disputing this part of it?

The part we are now disputing is this:
Same scenario as above EXCEPT Child #2 DOES have sibling preference. Who gets the spot then if both children have sibling preference but Child #1 ranked the school #3 and didn't get into 1-2, vs. Child #2 who ranked the school #1?

If you believe parent ranking has no effect beyond what order the computer tries to place you, you believe basically that at this point it's random. Those of us saying parent ranking matters are saying that in THIS scenario, Child #2 will get the spot. Hands down. And random computer assigned lottery number does not impact anything at this point.

I believe this because it's true.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

That is obvious. No one in any of these threads is disputing this.

Are you reading the same thread? People are questioning this on every page. People are stating that the parent ranking hold the more weight then it actually does. Go back to each page and you'll find at least one post where someone is saying having a school ranked #1 gives you priority over someone who ranked it #2 but with a better preference. That is not at all true and misrepresents a stable matching algorithm.

You conveniently cut out your post that I was responding to. Wow, are you that desperate to appear right?

Since you seem to have forgotten what you said:

Anonymous wrote:

Here's what putting a school at #1 does - it makes it your #1 school choice. If you get accepted in it, then great. If you don't then it moves down the line. It says, "I prefer this over the other schools I selected, so if I get in, I want to keep it". Your #2 school says "I prefer this over the other schools I selected accept for #1, and if I get into #2 then great! If I get into #1 then disregard #2 and give me #1".

You do not raise the bigger question that we are all arguing about in this quote. That is why THIS is obvious.

So, show ANYWHERE in this thread where the part of the process that you describe above is questioned?

4 posts above this (from 11:49) provide an example from page 14 where someone gets it wrong and assume a parent who ranks a school as #1 has greater weight than a parent who ranks the same school as #4.

Great, at least we're in agreement about this: no one is questioning what you said in the quotes. Because even the example you give here is not the same as what's in the quotes. Or do you not even understand what you yourself wrote?

Quite a few people are questioning it. What i say above is all that the student/parent ranking provides. I am saying this very clearly - IT PROVIDES NOTHING ELSE. Any question about what the parent ranking does is answered in my post above.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:
Child #1 has sibling preference but ranked school ABC at #3, and didn't get into their #1-2.
Child #2 has no preferences but ranked school ABC at #1.

Who gets the seat at school ABC?

What if child #2's lottery number is higher than child #1's?

Child #1. Sibling preference trumps no preference every time.

I second this. 100% according to the logic of stable match. School ABC prefers Child #2 over #1 so this creates an equitable match for all parties involved.

We were arguing this point yesterday, but as of yesterday, who is disputing this part of it?

The part we are now disputing is this:
Same scenario as above EXCEPT Child #2 DOES have sibling preference. Who gets the spot then if both children have sibling preference but Child #1 ranked the school #3 and didn't get into 1-2, vs. Child #2 who ranked the school #1?

If you believe parent ranking has no effect beyond what order the computer tries to place you, you believe basically that at this point it's random. Those of us saying parent ranking matters are saying that in THIS scenario, Child #2 will get the spot. Hands down. And random computer assigned lottery number does not impact anything at this point.

If the students are equal in terms of preferences, the one with the better number will get the spot, no matter what ranking the parent put.

[Anonymous]

Anonymous wrote:

Anonymous wrote:The school rankings made by other parents/student have absolutely no affect on your capability of accepting a seat in the lottery. The only thing has an affect on your acceptance is as follows:

1) Someone with a better preference requests the same seat
2) You get accepted at a higher ranked school.

That's it. It doesn't matter what the rank of the school was in scenario #1. The algorithm ignores it. It's entirely possible that the kid accepted in scenario #1 moves on to another school (that he ranked higher) and you can get the seat back! That's how the algorithm works!

Source? What is your source that in this specific situation it works this way?

This was all linked to earlier in the thread

Post article about MySchoolDC
http://www.washingtonpost.com/local/education/dc-rolls-out-unified-enrollment-lottery-for-traditional-charter-schools/2013/11/19/448ee1e0-4ca7-11e3-9890-a1e0997fb0c0_story.html

Which talks about Al Roth, nobel prize wining economist and chairman of IIPSC, the company running the lottery
http://iipsc.org/

The publication page leads to an article about the New Orleans Lottery
http://www.nola.com/education/index.ssf/2012/04/centralized_enrollment_in_reco.html

Which contains this image giving the steps on how the algorithm run
http://media.nola.com/education_impact/photo/diagram-enrollment-041512jpg-aea0b995c0aa929b.jpg

Pay special attention to step 3, because that's the crux of it. You are ranked by your preference pool and your random lottery number. Your school ranking only comes into play after step 3. The whole thing loops until it can't do any more matching.

If you really want to read up on it, here is an academic paper also published on the IIPSC website:
https://www2.bc.edu/~sonmezt/sc_aerfinal.pdf

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:
Child #1 has sibling preference but ranked school ABC at #3, and didn't get into their #1-2.
Child #2 has no preferences but ranked school ABC at #1.

Who gets the seat at school ABC?

What if child #2's lottery number is higher than child #1's?

Child #1. Sibling preference trumps no preference every time.

I second this. 100% according to the logic of stable match. School ABC prefers Child #2 over #1 so this creates an equitable match for all parties involved.

We were arguing this point yesterday, but as of yesterday, who is disputing this part of it?

The part we are now disputing is this:
Same scenario as above EXCEPT Child #2 DOES have sibling preference. Who gets the spot then if both children have sibling preference but Child #1 ranked the school #3 and didn't get into 1-2, vs. Child #2 who ranked the school #1?

If you believe parent ranking has no effect beyond what order the computer tries to place you, you believe basically that at this point it's random. Those of us saying parent ranking matters are saying that in THIS scenario, Child #2 will get the spot. Hands down. And random computer assigned lottery number does not impact anything at this point.

If the students are equal in terms of preferences, the one with the better number will get the spot, no matter what ranking the parent put.

Notable that of all the people saying this, none of you have provided a source yet for why this specific point is true for this DC Common Lottery. Interesting, and frankly, makes every opinion that says parent ranking doesn't affect this scenario totally suspicious.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:
Child #1 has sibling preference but ranked school ABC at #3, and didn't get into their #1-2.
Child #2 has no preferences but ranked school ABC at #1.

Who gets the seat at school ABC?

What if child #2's lottery number is higher than child #1's?

Child #1. Sibling preference trumps no preference every time.

I second this. 100% according to the logic of stable match. School ABC prefers Child #2 over #1 so this creates an equitable match for all parties involved.

We were arguing this point yesterday, but as of yesterday, who is disputing this part of it?

The part we are now disputing is this:
Same scenario as above EXCEPT Child #2 DOES have sibling preference. Who gets the spot then if both children have sibling preference but Child #1 ranked the school #3 and didn't get into 1-2, vs. Child #2 who ranked the school #1?

If you believe parent ranking has no effect beyond what order the computer tries to place you, you believe basically that at this point it's random. Those of us saying parent ranking matters are saying that in THIS scenario, Child #2 will get the spot. Hands down. And random computer assigned lottery number does not impact anything at this point.

If the students are equal in terms of preferences, the one with the better number will get the spot, no matter what ranking the parent put.

Notable that of all the people saying this, none of you have provided a source yet for why this specific point is true for this DC Common Lottery. Interesting, and frankly, makes every opinion that says parent ranking doesn't affect this scenario totally suspicious.

It's not true because that's not how a gale/shapely algorithm works.

[Anonymous]

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:

Anonymous wrote:
Child #1 has sibling preference but ranked school ABC at #3, and didn't get into their #1-2.
Child #2 has no preferences but ranked school ABC at #1.

Who gets the seat at school ABC?

What if child #2's lottery number is higher than child #1's?

Child #1. Sibling preference trumps no preference every time.

I second this. 100% according to the logic of stable match. School ABC prefers Child #2 over #1 so this creates an equitable match for all parties involved.

We were arguing this point yesterday, but as of yesterday, who is disputing this part of it?

The part we are now disputing is this:
Same scenario as above EXCEPT Child #2 DOES have sibling preference. Who gets the spot then if both children have sibling preference but Child #1 ranked the school #3 and didn't get into 1-2, vs. Child #2 who ranked the school #1?

If you believe parent ranking has no effect beyond what order the computer tries to place you, you believe basically that at this point it's random. Those of us saying parent ranking matters are saying that in THIS scenario, Child #2 will get the spot. Hands down. And random computer assigned lottery number does not impact anything at this point.

If the students are equal in terms of preferences, the one with the better number will get the spot, no matter what ranking the parent put.

Notable that of all the people saying this, none of you have provided a source yet for why this specific point is true for this DC Common Lottery. Interesting, and frankly, makes every opinion that says parent ranking doesn't affect this scenario totally suspicious.

You want something else to read? How about this http://www.nobelprize.org/nobel_prizes/economic-sciences/laureates/2012/popular-economicsciences2012.pdf

Go to the section titled "Matching students and high-schools". It says that what you believe is correct is not at all right and leads to gaming the system.

Since schools were more likely to admit students who
ranked them as their first choice, students unlikely to be admitted to their favorite school found it
in their best interest to list a more realistic option as their first choice, while applicants who simply
reported their true preferences suffered unnecessarily poor outcomes. In 2003, Roth and his colleagues
helped redesign this admissions process, based on an applicant-proposing version of the Gale-Shapley
algorithm. The new algorithm proved to be successful, with a 90 percent reduction in the number of
students assigned to schools for which they had expressed no preference. Today, a growing number of
U.S. metropolitan areas use some variant of the Gale-Shapley algorithm.

Now, go back to the links posted above and read about Gale/Shapely. At no point is the parent/student ranking brought into acceptance. It's only used to determined if they could get into a higher ranked choice. It has nothing to do with the actual acceptance procedure.

[Anonymous]

So is the logic:

Choose applicants with preference = sibling.
Of that result set, choose applicants where ranking = 1.
Of that result set, order by lottery number.
Award seats to applicants in that order.
If seats remain, choose applicants with preference = sibling and ranking = 2.
Of that result set, order by lottery number.
Award seats to applicants in that order.
Etc. down the ranking pools.

Or is it:

Choose applicants with preference = sibling.
Of that result set, order by lottery number.
Award highest possible ranked seat selected by each applicant in that order.