On: The price of solar power just fell 50% in 16 month...

[bemmu]

Hmm, I tried playing around with this tool.

When I enter 250000 in sample size I get ranges that don't overlap. Does that mean I would need that many samples to answer this?

[cscheid → bemmu]

Yes. The bigger your sample size, the bigger your ability to see small effects. A test with 1000 elements can only tell apart big effects; a test with 250000 can tell apart much smaller ones. This is the idea of https://en.wikipedia.org/wiki/Statistical_power