Diamond Enthusiast

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Well, since you asked for a critique...
My main concern would be the lack of a statistical analysis. I notice that you excluded "old black people" due to only having 1 member of that group. That was good. However, you did consider a group of only 9 ("black males"). My back-of-the-envelope calculation suggests that there is no statistically significant difference between this group and "white males" or "black females."* In fact, most of the differences between groups do not look statistically significant to me. For those that do, there is the problem of separating variables. Again, separating the people by more than one characteristic was good, but you did not go far enough. Your results (although, as I said, they mostly don't look statistically significant) suggest that race, age, and gender all have an impact. Separating by only two of these variables at a time still leaves room for comparisons between samples biased in the third variable. You could break the results down further, sorting by all three variables at once, but you'd have even smaller sample sizes and even less statistical significance. You could also use multiple regressions, but I'm sure you'd have a similarly low statistical significance. To make this experiment good, the main things you need are a much larger sample size (so that you can assure that your subsamples have large sample sizes) and a statistical analysis of the results.
Other concerns are as Claire noted - controlling the untested variables. Behavioral research is difficult to do well because there are so many variables which the experimenter can't control and may not even be aware of.
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*Back of the envelope calculation for "black males" gives +/- 33% at the 95% confidence interval, which means that there's a 95% chance that the true "honest" percentage lies somewhere between 11% and 77% (and a 1 in 20 chance that it's outside of that range). The other groups will have a narrower range due to larger sample sizes, but there is certainly no statistical difference between "black females," "white males," and "black males." Even the "white females" / "black males" comparison looks to me like it is on the edge of statistical significance. You'd have to do the calculations to determine on which side of the divide it lies (keeping in mind that the 95% standard is somewhat arbitrary and, by definition, is wrong 1 in 20 times). All that, of course, assumes that random sampling is the only effect and that other variables (age or location, for example) are not biasing the results of a particular comparison (as discussed earlier).
You'll need to drop a lot more wallets to get meaningful results.
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