This version of the free WordPress plugin Redirect URL to Post comes with a new feature: You can now pick a random from all posts with a bias on a certain subsample.
You determine the subsample as before with the parameters count and (optionally) offset. Normally, the random post would be picked from this subsample. If you, however, also use bias, the random post can be any of all posts. Those posts among the subsample will be more likely with a percentage1 as defined in bias.
With a probability of 80%, the random post will come from the most recent 10 posts.
With a probability of 50%, the random post will come from the oldest 10 posts, shifted by 5 posts from the end.
Install the plugin from the administration of your site or download it from WordPress.org.
Photo by annca