In Mechanical Turk, how do you limit to one HIT per worker

Question

Hi all, I know from communication with Mechanical Turk workers that there is a way to limit the number of HITs a specific worker can complete, but I cant figure out how to do it. Any help would be greatly appreciated!

Answer 1

See

http://docs.amazonwebservices.com/AWSMechanicalTurkRequester/2008-08-02/

You can set two types of limits:

• The maximum number of assignments any Worker can accept for a specific HIT type you've created. This value is undefined until you set it.
• The maximum number of assignments any Worker can accept for all your HITs that don't otherwise have a HIT-type-specific limit already assigned. The initial default value is 10.

Initially, all your HITs are grouped together with an overall limit (default of 10) applying to the group, regardless of HIT type.

Note that this refers to the number of assignments that a worker can have currently accepted. Once the worker has submitted an assignment, they can accept another assignment.

You probably shouldn't care how many HITs a worker completes overall, but there might be a reason why you want to change the number a worker can have currently accepted from the default 10. Of course, a worker can only accept one assignment from a HIT with multiple assignments.

If you really, really want to limit the number of HITs a worker can actually do, you're going to need to either specify that you're not going to accept more than a certain number per worker, explicitly stating that you're going to reject any submissions once the limit has been reached OR you could monkey with qualification types to do that (but that could be a lot of work)!

As an example of the latter, if you want to limit someone to doing N total assignments, you could a qualification type for each HIT and grant no more than N types to any one worker.

Answer 2

You can also do this with external questions. I run psychology experiments on mechanical turk, so I need unique participants. In addition to requesting that workers only perform one HIT, I use a python script to verify uniqueness. My HITs all run a cgi script to produce the question. The script consults a log file, and if the worker has previously accepted a related job, it politely informs them that because I need unique participants, the HIT won't be available.

I used to do this with qualifications, but found that it really limited participation.