Projects From Interviews/ Typical or Sham?

Hey guys I just want to know your opinion about being asked at an interview to work on a project as a test for hire. I was asked a few times in my career to come up with some concepts or actually do work for a day then afterwards the employer would choose which candidate for hire in the upcoming weeks. The work looks kind of specific and the thought would be that they are just looking for free concepts. How would you identify a sham from something that could be typical. thoughts.

See if this thread answers your question.

thx for the link