Poll-what countries use Delphi?

[Ryan_Todd]

Originally Posted by GMeyer

EricH's prediction was correct. Nearly 80% of the responses came from the United States, as can be seen in the attached pie graph.

I beg to differ!

If we use EricH's estimates, we would expect 3000/3150 = 95% of all responses to come from North America. Instead, the poll showed 85% of all responses originating in North America.

I don't care to dredge up enough memories of my statistics courses to run the confidence interval on a data sample of this size (that is left as an exercise for the reader), but if anything I'd say that these stats seem to show that CD is skewed towards international teams.

[gblake]

Shouldn't Texas be listed separately?

[GMeyer]

Originally Posted by Ryan_Todd

I beg to differ!

I don't care to dredge up enough memories of my statistics courses to run the confidence interval on a data sample of this size (that is left as an exercise for the reader), but if anything I'd say that these stats seem to show that CD is skewed towards international teams.

You're not wrong here, and you raise a good point. I do wish I had a larger sample size. But that turned out not to be the case, and responses had pretty much stopped coming in by the time yesterday came around, so I had to run with these results. Also, when I said that EricH's prediction had been "correct," I meant that the general point of his prediction- that results would be skewed towards the US- was correct. I should have specified this in the original post.

And I still think that point pans out. While the US did under perform, as you noted, it still took a much larger chunk of the pie than anyone else did. 79.8% of the responses were from the United States. Even if that is much less than 95%, the number EricH predicted, it still blows out the second biggest chunks of repondants- Canada and Israel, both with 5%.

If the US's 79.8% was much less than expected, I think this can be attributed to the relatively small sample size. If I had more responses, I think the results would be much closer to 95%.

[sdangelo]

Originally Posted by Ryan_Todd

I don't care to dredge up enough memories of my statistics courses...

I'll do the statistics!

First off, we have to assume that the responses were a random sample of ChiefDelphi users. In reality, they almost certainly weren't--this was a voluntary response survey, which are usually terrible at imitating randomness (for example, maybe non-US members would be more inclined to answer because they want to represent their country). But for the sake of calculations, we'll pretend that it is.

The FRC 2015 season facts flyer says that 87.2% of FRC teams last year were in the US. To use this as our percentage of ChiefDelphi members who theoretically would live in the US, we need to assume that there is no difference in the average team size between the US and the rest of the world, all ChiefDelphi members are FRC members , and the percentage of teams in the US hasn't changed since last year.

Assuming all of the above are true or negligible: if ChiefDelphi members' nationalities represented FIRST as a whole and the true proportion of ChiefDelphi members who are from the US is 87.2%, then the likelihood that 79.8% or less of 119 respondents would have been from the US is only 0.8%. This is very strong evidence that ChiefDelphi members are disproportionately from outside of the US.

Again assuming all of the above stipulations, we can be 95% confident that the true proportion of ChiefDelphi members who are from the US is between 72.6% and 87.0%. Whether this is a large enough difference to matter in strategy discussions, I can't say.

[GMeyer]

Originally Posted by sdangelo

I'll do the statistics!

First off, we have to assume that the responses were a random sample of ChiefDelphi users. In reality, they almost certainly weren't--this was a voluntary response survey, which are usually terrible at imitating randomness (for example, maybe non-US members would be more inclined to answer because they want to represent their country). But for the sake of calculations, we'll pretend that it is.

The FRC 2015 season facts flyer says that 87.2% of FRC teams last year were in the US. To use this as our percentage of ChiefDelphi members who theoretically would live in the US, we need to assume that there is no difference in the average team size between the US and the rest of the world, all ChiefDelphi members are FRC members , and the percentage of teams in the US hasn't changed since last year.

I'm starting to question my initial readings of the results, but I'm still not totally sold on this yet. Don't all of those assumptions sound like pretty big assumptions to make?

[sdangelo]

Originally Posted by GMeyer

I'm starting to question my initial readings of the results, but I'm still not totally sold on this yet. Don't all of those assumptions sound like pretty big assumptions to make?

Of course, that's why I pointed them out; I wanted anybody reading to take the results with a grain of salt. Unfortunately, these kinds of problems are much harder to fix than the sample size--which was actually more than large enough.

[Cabey4]

maybe non-US members would be more inclined to answer because they want to represent their country.

I think that that is definitely true. I know that that's why I'm here