On the data science side, it happens as well.
My response to them depends on the other details within the job posting. If they are asking questions that I notice directly correlate to "free work" then I won't apply to the project.
For most "what variables would you control for" type questions, I won't apply. Or I may give them an example of something I've completed in the past =
"For example, when I pulled x training data and y test data, I constructed this particular model. But, each use case scenario is different depending on the type of data and your purpose for the model (e.g. what question are you trying to answer or behavior you're trying to predict?). I'll be happy to discuss further details with you through the interview process to gain a clearer picture of the scope of work."
I write resumes and I run into much of the same. People want me to explain exactly what changes I will make to their resume. I tend to answer in generalities, and have in the past gone so far as to say that I couldn't be more specific without giving away my work product. I also worry about this when I am asked for job-specific samples - it is my work, but doesn't stop anyone from putting their info and jobs on it. I think it's an interesting position since anyone can pull a resume sample off the internet and claim it as their work.
I notice this too -- and I will respond:
"I have an idea of precisely how to solve your problem, am eager to show you after I am awarded the project and it is fully funded." Finish it off with "What do you think?"
If they are genuine AND if they are still considering you, they will oblige. Difficulty is knowing what is behind their lack of response.
SIDE NOTE: I just this week had a potential valuation client ask me for an Excel valuation model (in the real world, not online). It happens everywhere and with more regularity: people seem more brazen and less ethical than ever.
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