Impact factor system in Voofie

Impact factor system on Voofie is a rating system based on three principles:

• Experts are more knowledgeable about the quality of the posts, hence they should have a greater influence on ratings;
• Different users have different expertise, hence experts of related fields should have higher authority than experts of unrelated fields
• User may have multiple focus areas, hence you will have a measurement of your authority on each subject areas

By using the three principles, Voofie has designed an impact factor system to identify experts and good posts. By having a higher impact factor, your posts and comments will seem more trustworthy than the users having a lower impact factor.  You will also become more notable as you will have a higher ranking in the searching results.

How does it work?

Each user and each post will have their own impact factor.  The following figure shows an overview of how the system works.

How experts can be identified in Voofie

Impact factor for posts is a measurement of popularity or importance.  Posts that are frequently viewed, rated and commented will have a higher impact.   Basically, good posts that draw attentions will receive a high impact.  Posts that attract experts will also have a higher impact than those attracting laymen.

However, popular posts do not imply good quality.  Therefore, besides impact, there is also a rating for each posts reflecting the quality of posts.  Unlike other sites, rating on Voofie is not a simple average of all ratings, but a weighted average of rating, weighted by the impact factor of users who rated.  Hence, users with higher impact will have higher authority in determining the rating of posts.  (see section below)

Meanwhile, your impact factor reflect your authority, reputation and contribution.   It is based on the rating and impact of all your posts, including Articles, Questions, Discussions, Links, Comments and Answers.  You can gain impact by submitting quality, popular, trustworthy and original posts.  As different users have different expertise, there is an impact factor for each concept tag that is used by you.  Hence, we are able to discriminate users’ contribution level in specialized fields such as AJAX programming, Tort law or Credit Default Swaps.

Use of Expert Judgements

In Voofie, not all users have the same authority in determining the impact factor of other users.  In this case, there are two important considerations so that the impact factor and ratings can better reflect the experts' consensus.

Considerations for experts in different fields

How to account for differences in expertise?

As there are over 3 million concept tags in Voofie, users may not have the impact factor in the same field.  For instance, an expert in Java Programming Language should be knowledgeable enough to assess the quality of a post about C++ Programming Language.  Also, an user with high authority in a specialized field such as Credit Default Swaps should also have a good authority in the corresponding generalized concept, which is finance in this case.  Meanwhile, a Biology expert should have low authority in rating a C++ post.  Hence, relations between concepts should be taken into account when determining who have a higher authority to rate the post.

The relations between subjects are measured by Semantic Relatedness, which is a quantitative measure of how two concepts are related.  The measure is calculated using our analysis of the corresponding Wikipedia article, in which page link, category and other useful information are used to generate a relatedness measure of any two given concepts.  In most cases the Semantic Relatedness between two unrelated concepts is zero, so expert of an unrelated field will have a low authority.

Consideration for multiple impact factors in different fields

Expert's Authority

As users gain impact factor on each concept tag they used, each users may have multiple impact factor, hence it is important to consider all of these impact factor records in order to give a fair assessment on the true authority on a given post.  When users rate a post, all impact score of different concepts will be considered.  Impact factor of each concept will be discounted according to the degree of relatedness between the concept and each of the concept tags for the post.  The figure below show an example of how authority of users can be determined. 

In this example, User 3 submitted a post with tag B, C and D, hence the rating and impact of the post will contribute to User 3’s impact factor of B, C and D.   When User 1 rate the post, authority contributed by impact factor of concept A will first considered according to the relatedness between A and tags of the post.  So, impact factor of A for User 1 will be discounted according to the relatedness of A-B, A-C and A-D.  Similarly, authority contributed by impact factor of B and C will be considered in the same manner.  Authority contributed by A, B and C will be added to give final authority on the post for User 1. Assuming impact factor for A, B, C for User 1 and X, Y, Z for User 2 is the same, as User 1 has a skill profile more related to the post than User 2, User 1 will have a higher authority and hence a higher influence to rate on the content.  By allowing experts of the field to have a higher power, the rating can better reflect the real quality of the post.

Strategies to Maximize your impact

1) Posting good work.  When others find your work useful, they will view your post often and rate it high.

2) Think before you tag.  The way you tag decides how the post reaches its audience and how you gain impact factor.  Try tagging your post with one general concept tag, two specific concept tags and suitable attribute tags to help users finding the post.

3) Don't be afraid to specialize.  Although posts about general or introductory topics attract more audience, specialized posts that attract experts in related field will gain impact quicker as well as experts contribute higher impact per page view.