What am I?

Q: How many post-doctoral fellows does it take to change a lightbulb?
A: One, but it'll probably take three or four tries to get it right because he/she will probably give it to the technician to do.
Q: How many graduate students does it take to screw in a light bulb?
A: Only one, but it may take upwards of five years for him to get it done.
Q: How many graduate students does it take to screw in a light bulb?
A: It all depends on the size of the grant.
Q: How many graduate students does it take to screw in a light bulb?
A: Two and a professor to take credit.
Q: How many graduate students does it take to screw in a light bulb?
A: 1/100. A graduate student needs to change 100 lightbulbs a day.
Q: Do you know how many musicians it takes to change a light bulb?
A: Twenty. One to hold the bulb, two to turn the ladder, and seventeen in on the guest list.
Q: Do you know how many musicians it takes to change a light bulb?
A: Five. One to screw in the light bulb and four to stand around and say, "Man, if I'd had his studio time, I could have done that."
Q: Do you know how many musicians it takes to change a light bulb?
A: 5, one to change the bulb and 4 to get in free because they know the guy who owns the socket.