Invincible (Skillet album) Invincible (Skillet album) Invincible is the third studio album by American Christian rock band Skillet. It was released in 2000 from ForeFront Records and Ardent Records. This album continues the electronic rock that was heard on their previous release but marks the exit of original guitarist, Ken Steorts, and the entrance of his replacement, Kevin Haaland on guitar, as well as John Cooper's wife Korey on keyboards, loops, sampling and programming. All songs written by John L. Cooper, except where noted. There was a music video made for the song "Best Kept Secret". It was the first video by the
Differential item functioning Differential item functioning Differential item functioning (DIF) is a statistical characteristic of an item that shows the extent to which the item might be measuring different abilities for members of separate subgroups. Average item scores for subgroups having the same overall score on the test are compared to determine whether the item is measuring in essentially the same way for all subgroups. The presence of DIF requires review and judgment, and it does not necessarily indicate the presence of bias. DIF analysis provides an indication of unexpected behavior of items on a test. An item does not display DIF if