In his letter, Dr Noonan includes a post hoc power analysis. However, his analysis is meaningless with respect to the statistical significance of our results. Current statistical convention dictates that post hoc power analysis should not be performed because it is fundamentally flawed, does not provide any meaningful information, and may be misleading.2-6 There are a number of reasons for its inappropriateness. First, post hoc power analysis can mislead the reader into concluding that an observed result is a false-negative caused by type 2 error, by incorrectly implying that a low post hoc power is caused by “too few” subjects. Apparently, this is what Dr Noonan has attempted to imply. However, once a statistically insignificant result has been obtained, the effect of sample size and associated variance should be obtained from information within the 95% CI, not by post hoc power analysis.2-6 In addition, calculated power has relevance only when the null is known to be false. To calculate post hoc power for a statistically insignificant result requires one to make a biased assumption that the null is false, even though it is already known that this assumption is not supported by the data. This is “nonsensical.”3 Furthermore, a statistically insignificant result will always result in a low post hoc power. That is, P ≥ .05 will always produce a post hoc power ≤ 0.5, regardless of how large or small the sample size is. This is because post hoc power is directly related to the P value mathematically. In fact, the greater (less significant) the observed P value, the lower the post hoc calculated power. Thus, the basic logic of using post hoc power analysis is convoluted and fundamentally flawed. In this regard, calculating post hoc power adds no new information once the P value is known4,5; it simply tells us what we already know. With respect to our study, Dr Noonan’s post hoc power analysis simply tells us that our data analysis does not detect a statistically significant difference in mean lung function data between the miner group with pleural plaques alone and the miner group with normal HRCT scan studies. Again, this result is supported by information contained within the 95% CI.