This is the archive of tumbledry happenings that occurred on 25 November, 2009.

Steve commenting on When Information Overwhelms Facts

In the source page for the SquareTrade report, the first citation is literally “We’re guessing on all this data.”

John commenting on When Information Overwhelms Facts

You do realize that your article is invalid and shows that you have no appreciation for statistics?

1. You cannot get a negative mean to the failure rate. The up-side is capped presumably at 100%. For a mean of ~20%, this infers that a likely maximum stdev = around 10%. Factoring in the situation that the true mean may be on the top-side instead, the maximum stdev = around 40%. That means that an assumed stdev ~15% - 25% is extremely liberal, and can be used as proxy for the maximum actual stdev (much more likely to be smaller).
2. You have n = 30k.
3. You can calculate maximum stderr from assumed stdev and n, which proves that all numbers are actually statistically significant at 95%.

Do the calculation yourself.