I've had some experience with using interns in test groups over the past eight years. What I want to do is present two cases - one that worked poorly and one that is working well - and then draw a few test-group-specific conclusions.
In the late 1990s Hewlett Packard had a program (they probably still do) called SEED: Student Employment and Educational Development. Every summer the company hired standout undergraduate students as summer interns. In my division it was a very organized program, the students hired were bright and articulate, and several of the people I worked with were former SEEDs themselves.
One summer my test group retained a SEED intern - let's call him Bill. Bill was a smart guy pursuing a BS in CS at a great school. He had a good deal of experience with designing web sites and JAVA programming (which had only been released a couple of years before). He even did some volunteer work for Red Hat debugging Linux - they gave him stock options which paid out very well when Red Hat went public in 1999. In other words, he was a very clever computer geek.
Bill did very well with one project he was assigned. The tasks were a) write a JAVA program that interfaced with a spectrum analyzer, b) repeadedly run the analyzer through a series of rigorous tasks, c) track the free memory of the analyzer over a long period of time, and d) find any memory leaks and what triggers them. He wrote the program, ran it, and found some important problems.
Bill liked programming, but he wasn't interested in data analysis, hardware (EE stuff) or miscellaneous paperwork. When he had to do those tasks he performed poorly. For example, when he was asked to analyze some data from a series of tests, I spent a lot of time walking him through using advanced features in Excel. If I wasn't there showing him what to do and how, he would tend to chat online with friends and play games. He needed a lot of supervision and guidance.
To be fair, one of Bill's problems was a lack of planning on the manager's part. In my opinion, he didn't always assign tasks that played to Bill's strengths, and sometimes the goals and steps towards those goals were vague. But at the end of the day it was Bill's responsibility to try and figure out things he didn't understand, and to actively seek out help when he needed it (instead of spending the day playing Diablo).
Part 2 of 3 will talk about a successful intern.
Part 3 of 3 will draw a few conclusions.