Tools to make random choices, generate random numbers, etc. Random Selection is a way to make a choice by computer randomization.

Random Selection - dCode

Tag(s) : Fun/Miscellaneous, Algorithm, Combinatorics

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A draw is a way of leaving a decision to chance, such as selecting one or more items from a list.

To randomize a choice or create a sweepstake in this generator, enter elements to pick and the number of items to select, the program will generate the list of winning/lucky items randomly. This generation/randomization is done without bias and uses a pseudo-random generator (PRNG).

Without a list or with too many items, assign a number on objects/people and use the random number generator.

__Example:__ The list `Tails,Head` (2 items) will return on average 50% of the time `Head` (once in 2) and 50% of time `Tails` (once in 2).

The list of items can be given in 2 formats: either one item per line, or all items at once but, in this case, items must not contain spaces.

In many countries, it is not longer mandatory to go through a bailiff to file the settlement and result of a game/contest/lotto/tombola/lottery. In order to avoid disputes it is advisable to draft a rule, and to prove the draw, the simplest is to cast it live (easy on Youtube, Instagram, Twitter or Facebook).

If a regulation is written, use something like:

*Free contest [with/without] purchase obligation from yyyy-mm-dd at 00:01 until yyyy-mm-dd at 23:59 [indicate timezone], limited to one entry per person. Participation in the game is via [indicate how to participate: fill out a form, send a message, leave a comment, etc.]. The draw will take place on yyyy-mm-dd on the dedicated website https://www.dcode.fr/random-selection [indicate the process used: by incorporating the names of the participants or by drawing a number between 1 and N with N the number of participants numbered chronologically].*

If an item is present multiple times in the list then it is more likely to be selected.

__Example:__ To get `A` 3 times more often than `B`, use a list `A,A,A,B` (4 items) that will return 75% of the time `A` (3 out of 4) and 25 % of the time `B` (1 out of 4)

If the chances of draws should be equiprobable for all participants, use a tool to remove duplicates.

Without replacement, an item cannot be selected more than once in a draw of multiple items. The picked element is not put back in the pile of the selectable elements, it is set aside, it is the case on most random selection processes.

__Example:__ The draw among `A,B,C` of 2 elements **without replacement** can give `A,B`, `A,C` or `B,C`, but never `A,A` or `B,B`. Because there is no replacement of the first drawn element, it can not be drawn a second time.

With replacement, if multiple items have to be selected, then items are picked one after the other and replaced in the item list to select and thus, they can appear more than once.

__Example:__ The draw among `A,B,C` of 2 elements **with replacement** can give `A,B`, `A,B`, `A,C` or 'B, C', but also `A,A` or `B,B` or `C,C` because the first element is returned to the list after the first draw and can be output a second time.

From a lower limit (minimum) and an upper limit (maximum), the randomizer generates a number automatically in the interval.

__Example:__ To make a Youtube/Instagram/Twitter draw among 100 comments/followers, set the random picker to select a number between 1 and 100.

The program is limited to natural integers. To get a decimal number between 1.5 and 2.5 ask for a number between 15 and 25 and divide by 10 or between 150 and 250 and divide by 100.

The dCode randomizer can generate groups (or pairing groups) depending on the group size or the total number of groups.

__Example:__ In a set of 6 elements, the program can create groups of size `2` (ie 3 groups of 2) or create a set of `2` groups (ie 2 groups of 3).

dCode can generate a bijection af a group 1 in a group 2. Input all two groups one after the other.

__Example:__ To create random matches in pairs (see also the round-robin championship generator), or assign tasks, describe the group 1 `A,B,C` and the group 2 `D,E,F` and the program will generate 3 encounters, for example `AF,BD,CE`

The dCode random picker generator can assign each person to another (distinct of itself), which is useful for Christmas gifting (only the draw is free, not the gift).

__Example:__ With the group `A,B,C,D,E`, dCode could propose as assignment `A->C,C->B,B->E,E->D,D->A`

First create groups of similar level (first the seeds, then etc.) of the same size N, then randomly associate to each item of a group a random number (from 1 to N). Each item having the same number is in the same tournament pool. See Round Robin Generator or the Tournament Tree Generator.

dCode retains ownership of the "Random Selection" source code. Except explicit open source licence (indicated Creative Commons / free), the "Random Selection" algorithm, the applet or snippet (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, translator), or the "Random Selection" functions (calculate, convert, solve, decrypt / encrypt, decipher / cipher, decode / encode, translate) written in any informatic language (Python, Java, PHP, C#, Javascript, Matlab, etc.) and all data download, script, or API access for "Random Selection" are not public, same for offline use on PC, mobile, tablet, iPhone or Android app!

Reminder : dCode is free to use.

The copy-paste of the page "Random Selection" or any of its results, is allowed as long as you cite dCode!

Cite as source (bibliography):

*Random Selection* on dCode.fr [online website], retrieved on 2023-01-30,

- Random Choice of Elements / People
- Random Number Generator
- Specific Random Selections
- What is a random selection? (Definition)
- How to make a random sample/selection?
- How to get a proof of the result?
- What are the legal mentions of a draw?
- How to ponderate the chances of selection?
- What is a random sample without replacement?
- What is a random sample with replacement?
- How to generate a random number?
- How to generate groups?
- How to associate items from two groups of the same size?
- How to assign people for gifting each other?
- How to create a tournament with seeds?

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https://www.dcode.fr/random-selection

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