Let's see how many days of the year we can fill with Doper Birthdays.

[Critical_Mass]

Add me for March 2

[Jake]

New Year’s baby. December 31.

[Marathon]

You can add me for January 27th (Mozart’s bday, too!)

[furlibusea]

December 21st

[sleeepy2]

October 21

[Elmo_Lincoln]

April 10 for Elmo Lincoln

[Sternvogel]

@marque elf

Statistically it supposedly works out that in any group of 30 people, 2 will have the same birthdate. … Can any explain to me why this is so?

Here is a site which explains the birthday problem.

[Uncommon_Sense]

@Sean Factotum

Well May 9th is still open as of the last update, so I’ll claim that.

Damn you. Is there room on that day for the two of us?

[kittenblue]

March 6

[One_And_Only_Wanderers]

Feb 10th.
Woohoo it hasn’t gone yet. I thought I would have to share for sure by now.

[Noone_Special]

@hajario

Not exactly. If you have a group of 23 people, it is more likely than not that at least two of the 23 have the same birthday. The easiest way to calculate this is to take 23 people and calculate the odds that none of the 23 have the same birthday. My stats book is too dusty and in a way to inconvenient place for me to do anything but leave the rest as an exercise to the reader.

OK, let’s run through this in a bit more detail…

1 guy – any of 365 days (let’s leave Feb 29 out of this for the moment). His “chance” of not “sharing” his birthday is 365/365, or 100%.
Chance that 2[sup]nd[/sup] guy does not share birthday with first is 1 - 1/365, or 364/365.
Chance that 3[sup]rd[/sup] person does not share a birthday with first two, assuing the first two were born on different days, is 363/365.

Now comes the hard part – the chance that #2 doesn’t share with #1 and #3 shares with neither is (364/365)(363/365); which is still darn close to 1. (this should technically be prefixed by "(365/365)" for the first person, but let’s not be silly…)

For the 23 rd person, the chance of having no shared birthday is (364/365)(363/365)(362/365)…((365-22)/365). Or - (364363362*…*343)/(365^22). Now it turns out the result of this calculation is 0.4927…, or just about 50%. So the 23[sup]rd[/sup] person in a random sample has a 50/50 chance of sharing a birthday with one of the other 22.

[surrotobeinMD]

August 19th

[chrisk]

@marque elf

Statistically it supposedly works out that in any group of 30 people, 2 will have the same birthdate. The first place I heard this was Let’s Make A Deal, perhaps not the most reliable of sources. Later I heard from a more reliable source. I never took statistics so I wouldn’t understand the math but intuitively this doesn’t seem right to me. Your odds for any specific birthday are only 1 in 365/366. Why does the probability drop down to 1 in 1 when 30 people are present? Each birthday is a random event. Shouldn’t then the probability be 1 in 365 times 2 times 30? That doesn’t equal 1 in my book.

Can any explain to me why this is so?

As people have pointed out, it’s not guaranteed that 2 will have the same birthday… it’s just a better than 50/50 proposition to take.

And, try thinking of it this way. Have your 30 people all shake hands, each person with every other person, and say their birthdays as they do so.

Each person has to shake hands with 29 other people. Since there are two people involved in each handshake, that means (30 * 29) / 2 or 435 distinct handshakes.

In each of those handshakes, there is a 1/365 probability that they will say the same birthday… (slightly less considering that there might be a leap baby in the group, slightly more if you allow for slight annual fluctuations in the birth rate.) From here on the math gets complicated, but it’s not too surprising that you have a fairly high probability of a match among those 435 distinct pairs.

Hope that helped.

[chrisk]

@marque elf

We have had 206 respondents for 160 days. That may not equal 1 in 365 but it is not far off from it either.

Not quite sure what you mean here… we’ve had over 40 collisions in a group of 200-some people, that’s a little outside the scope of the birthday paradox but it seems to support it.

And, keep in mind, there was a selection bias AGAINST people posting if they spotted someone already having their birthday (I think) because the OP was asking for people to try to ‘fill up days in the calendar’. If your day is already filled, then you’re not helping to accomplish that goal, though you do have a chance to say hi to someone else who shares your birthday.

[Theodore_Striker]

March 28th- that should knock another one out.

[Staggerlee]

2nd January for me, please.

[dasgupta]

Looks like I’m the third October 16[sup]th[/sup].

[Idle_Thoughts]

@marque elf

We have had 206 respondents for 160 days. That may not equal 1 in 365 but it is not far off from it either.

Don’t know if anyone answered this yet–when I update I read the replies one at a time, so I haven’t seen any reply after this yet–But 206 is actually the number of days we have represented. Not the number of people in here who gave me their birthday. 160 is the number of days still left that nobody has “claimed” yet.

[picunurse]

June 24th here. Hubby is April 8th

[Idle_Thoughts]

@chrisk

And, keep in mind, there was a selection bias AGAINST people posting if they spotted someone already having their birthday (I think) because the OP was asking for people to try to ‘fill up days in the calendar’. If your day is already filled, then you’re not helping to accomplish that goal, though you do have a chance to say hi to someone else who shares your birthday.

Yeah, tell me about it. See, this is what I was worried about and keep thinking every now and again. That people will come in and see that their day is already “taken” and therefore not reply. I would hope they wouldn’t do that, because their day could count for the “Random Stats” and change those…but I can’t force people to reply if they don’t want to.

All I can do is make this post. If you’re reading right now, or have already and are now just following along, and your birthday was already listed…so what? Reply anyway and be added to the number and say hi to the people who share it.

Random Stats:

Day with the most birthdays so far: July 29th has 5
Month with the most birthdays so far: July has 31
Month with the least birthdays so far: April only has 18
Number of days of the year so far: 217
Number of days still needed: 149
Biggest “run” in a row so far: 9 (December 11th - 19th)

January
1st- Athena, supervenusfreak, Nancarrow
2nd- Staggerlee
3rd- BlackKnight, Madd Maxx
5th- Honey
6th- Ravenman
9th- Small Clanger
13th- A.R. Cane
14th- Diceman
18th- saramamalana
19th- DiosaBellissima
20th- NurseCarmen
21st- ladyfoxfyre, gommsn
23th- dalej42
25th- Rhiannon8404
27th- Barrytown
29th- Governor Quinn, Elza B.

February
2nd- Happy Lendervedder
3rd- Mona Lott
4th- romansperson
5th- Hampshire
7th- Hal Briston
8th- The Sausage Creature
10th- One And Only Wanderers
11th- coop
12th- percypercy
13th- Rhythmdvl
14th- Cat Jones
16th- Aholibah
17th- Little Bird
19th- Enright3
20th- mikeargo
21st- stargazer
22nd- OliverTwistofLime, Jackknifed Juggernaut
23rd- ryobserver
25th- Craneop2
28th- Stillwell Angel

March
1st- Kyyrewyyoae
2nd- qwest
4th- FilmGeek
6th- kittenblue
7th- The Mad Hermit
8th- Sierra Indigo
11th- faithfool
12th- LoganDear
14th- straykat23
15th- TwoTrouts
16th- nonacetone, Jennshark
19th- Nymphadora, AuntiePam
20th- metj
22nd- CWN
24th- Mrs. Franchi
25th- Cerri
28th- Theodore Striker
29th- ultrafilter
30th- Brilharma
31st- Rockwell, MrsMonkey

April
1st- Astroboy14
5th- wolfstu
10th- SeeNoReason, elfkin477, Elmo Lincoln
11th- Waenara, Buckler of Swashing
12th- brightpenny
16th- Susie Derkins, Penchan, irishgirl
20th- AngelicGemma
23rd- BayleDomon
24th- jsgoddess
25th- percussion
26th- runner pat
28th- BrattiAtti, ZipperJJ

May
1st- Avarie537, PinkMarabou
3rd- chimichanga
6th- sneezy5660, Jpeg Jones
9th- Sean Factotum, Uncommon Sense
10th- Khadro, ladybug
11th- ErinPuff
12th- Art Vandelay, Architect
14th- Good Egg
15th- Nic2004
16tg- Cub Mistress
18th- cher3
19th- Marley23
21st- robotic_panda
24th- scr4
25th- Cunctator, MissTake
26th- LavenderBlue, Atheist Princess
27th- liberty3701
29th- Kilvert’s Pagan
31st- fruitbat

June
1st- ENugent, Ragiel
3rd- Miabella
2nd- Loach
4th- Demo
5th- sishoch
6th- Ponster
7th- Anastasaeon, Carm6773
8th- Cowgirl Jules
11th- mhendo
12th- Johnny L.A.
13th- Pixel
14th- Balle_M
15th- Shagnasty
16th- Epimetheus
18th- GorillaMan
22nd- Inigo Montoya
23rd- Arwin
24th- Barracuda
25th- Long Time First Time
26th- 1920s Style “Death Ray”, hillbilly queen, MsRobyn

July
1st- newcrasher, photopat
2nd- Taran
5th- Starlite, trublmakr
6th- World Eater, Absolute, mkl12
10th- jsc1953
11th- pulykamell
12th- eleanorigby
14th- Enginerd, Waterman
15th- Landshark, ShibbOleth
16th- Antonius Block
17th- Mr. Goob
18th- Kythereia
19th- gfloyd
20th- Emilio Lizardo
23rd- MrFantsyPants
24th- Dung Beetle
29th- Ayesha, Bear_Nenno, Ejs Girl, Kyla, Swambear
31st- Bird Man, Yeticus Rex, Vunderbob, krisolev

August
1st-moonstarssun, BraheSilver
2nd- Ninja Chick
3rd- Meaty Beaty Big and Bouncy, Mint Julep
4th- Suburban Plankton, Hokkaido Brit
8th- AntaresJB, pudytat72
10th- Ice Wolf
12th- Mighty Girl, Butterscotch
18th- psycat90
19th- Grasshopper, surrotobeinMD
21st- StarvingButStrong, Ludy, KJ
22nd- Hilarity N. Suze, akira5822
24th- Mr. Blue Sky
27th- Faruiza, Tamryne
28th- interface2x
30th- Sternvogel, cherry, Monstre
31st- VenusProbe

September
2nd- BitternessComesStandard
6th- bobkitty
8th- Lsura
9th- vivalostwages
12th- jrfranchi
13th- XWalrus2
14th- Johanna
16th- The Flying Dutchman, feppytweed
17th- Miss Violaceous
18th- WallFlower
20th- Canadiangirl, racer1
21st- Misnomer
23rd- Spikesbud
28th- TellMeI’mNotCrazy, Harimad-sol, Encinitas
29th- Crafter_Man
30th- Blalron, anyrose

October
1st- Eleusis, fishbicycle
3rd- racer72
5th- Nutty Bunny
6th- Manatee, Otanx
7th- malkavia, ltfire
8th- LaurAnge
10th- danceswithcats, Ellen Cherry
11th- PaperBlob
12th- Stinkum
13th- slai
14th- Martha, August West
15th- Ms Macphisto
16th- BadBadger, Antigen, dasgupta
18th- Smashed Ice Cream
19th- Spongemom
21st- sleeep2
22nd- Hentor the Barbarian
26th- Gail
31st- seosamh, dangermom

November
2nd- Harborwolf
3rd- jackelope
4th- Sassy
5th- YaWanna
6th- BwanaBob
7th- melondeca
10th- movingfinger, norinew
11th- EvilAsh
13th- marque elf, Jman
14th- Voyager
16th- Pyroette
17th- chrisk
18th- UncaStuart
20th- cat39645
22nd- Idle Thoughts
23rd- BiblioCat
26th- KSO, WhyNot
27th- DirtyHippy, Odinoneeye
30th- Noone Special, infamousmom, Anaamika

December
1st- Khadaji, Marconi & Schmeese, CalMeacham
2nd- Snakescatlady
4th- Zeldar, Mishell
9th- Misery Loves Co.
11th- PookahMacPhellimey
12th- Rushgeekgirl, Twoflower
13th- betenoir
14th- Corporate Hippie
15th- Lady Venom
16th- csharpmajor
17th- mr bus guy, detop
18th- PinkNailFile
19th- Clothahump
21st- furlibusea
22nd- Pandora
23th- PigBoy
24th- dare_devil007_
25th- Kat, Annie-Xmas
27th- MissGypsy
28th- amarone, picker
29th- dinahmoe
31st- Jake