Can someone explain me the math behind polls?

[terraboss (Markus)]

It’s a little bit confusing for me and others to understand the mathematical summary behind the percentages.

I’m the opinion that all answers per poll should result to 100% and not 200%. Even for two votes. That’s not logical.

Is this a bug?

[jomaxro (Joshua Rosenfeld)]

Wasn’t this just fixed?

Polls percentage accounting is not accurate

It seems when calculating percentage for each option in polls Discourse uses floats truncating instead of rounding. This can result into inaccurate percentage values. For instance, a poll with 2 options, 11 voters and votes spread as 5 for the 1st option and 6 for the 2nd option indicates 45% and 54% which is 99% in total but should be 100%. The math looks to be the following: 100/11*5 is 45.45, which rounded to 0 decimal places is 45, and also truncated to 0 decimal places is 45. 100/11*6 is…

[terraboss (Markus)]

I’m running the latest-release +59.

[gerhard (Gerhard Schlager)]

The meaning of that poll result is:

• 49% of all voters selected “Montags”
• 24% of all voters selected “Dienstags”
• …

This seems to be a multiple choice poll, so it is perfectly normal that the sum of the percentages is greater than 100%. But the -1% definitely looks like a bug.

[zogstrip (Régis Hanol)]

Yeah I will deactivate the “rounding up to 100%” on multiple polls. Nice catch

[zogstrip (Régis Hanol)]

@terraboss, I just pushed a fix for multiple choice polls

https://github.com/discourse/discourse/commit/9d2128dad30aaa96a0b13be666daabbbba2993f8