According to standard convention, a researcher must be ___ percent sure that the difference she observed between experimental conditions was not simply the result of chance in order to conclude that the difference is statistically significant.

Answer - 95 percent

As stipulated by standard convention, a researcher must have at least a 95 percent assurance that the difference which was observed by her between experimental conditions was not merely coincidental in order to justifiably conclude that the difference she observed has statistical significance.