# Randomizations and probability calculations

Dear Kobo team,

I’d like to see if there is a way to be able to use a formula which can:

1. Randomly choose an option amongst 3 options with an equal probability of 1/3 to be selected

2. Calculating a winning and loosing decisiob based on (1 draws, 1 as probability of winning loosing, chance as a percentage) for example binomial (1,1, 0.5)

@myriamdagher1, maybe this post discussed previously should give you some clue to your query:

Thank you Kal. Can you please share the image? I am not able to find it in your reply.

Please can you share the image you reffered to?

Hello,
random testing.xlsx (17.9 KB)
I created the attached sheet and I appreciate your feedback on the below:

1. Does the following expression: int(random() * 3) + 1 randomly choose between three options/groups (1, 2, 3) with equal probability for each option to be selected (1/3 probability for each)?
2. Does this expression if(random() <= 0.5, ‘Win’, ‘Loss’) calculate the winning/losing based on 1 drawing, same probability for winning and losing, and a specific chance?

Myriam.

Hint: random() as any calculation will be activated/updated any time you open/edit the case. Otherwise, you would need to pack the calculation with once(…).

If you want to simply randomize choices you can use the randomize=true appearance for the select. See (Question Types - ODK Docs).

Don’t forget, please, to always check your form with the Online validator,, during development and before deployment. It will for ex. show you that you should add the 2-letter language codes in the columns. See

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I copied your redundant new posting here. You can delete it there. Please, avoid posting for the same issue in more than one thread.

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Duplicate posting on the same issue, see https://community.kobotoolbox.org/t/randomizations-and-probability-calculations/47137. Please, keep in one main thread, also for following aspects on the same topic. You can edit your posts (pencil icon) or add new postings there to enhance/change your thread.

Thank you so much I used once(…) and the value generated did not change after loading the form!