In Studo Wiki you can collaboratively edit information about your courses to help your fellow students. Some information is free text where you can add your own tips. And some information is displayed as a weighted average.

## Weighted average

Recent votes on course/exam effort or difficulty might be more relevant to you if the course has changed curriculum or a new professor is teaching. To take this into account, Studo Wiki calculates the votes as a weighted average. This means that new votes count more than older votes. However, older votes are not lost if a course has only a few votes in a semester.

The weighted average is an exponential weighted step function:

**Exponential**: Votes from the last 365 days count 100%, votes from the 365 days before that count 50%, then 25%, then 12.5%, and so on. Therefore, if the course has the same number of votes each year, the votes from the last 365 days have the same weight as all other votes before that.

**Step**: Newer votes should count more than older votes. However, a vote from yesterday should not count more than a vote from two days ago, since both votes reflect the same semester. Therefore, the stepping is done on a per year basis: Votes from the last 365 days count 100%, and every 365 days votes lose half the weighting.

To be exact, the we use 365.2425 days to take account into leap years.