Add functions for power analysis

[leeper]

Please specify whether your issue is about:

• a possible bug
• a question about package functionality
• a suggested code or documentation change, improvement to the code, or feature request

Power analysis and sample-size determination could be useful. Some draft code from Hainmueller et al. is here: https://www.dropbox.com/s/xdamgzwl60h1b6w/conjointpower.R?dl=0

[mbarnfield]

I did some super basic stuff in my cjpwr repo based on this old documentation. Don't think this is anywhere near sophisticated enough, but it exists.

[leeper]

@mbarnfield What's your plan with that repo? Do you plan to put it on CRAN or maybe you'd be interested in folding something like that in to this?

[mbarnfield]

I'd be happy to integrate it into cregg. It definitely needs work though! If you're happy with the general approach in the Hainmueller code (which doesn't look that complex) then it might not be too much work to get cjpwr to that level, but tidier. I'm not sure what he's basing his approach on, though, and I'm not well-versed on power analysis in general.

[leeper]

Other resources:

https://www.robertkubinec.com/post/conjoint_power_simulation/

https://www.brettgall.com/post/conjoint-power-simulations/