Question

4.151 Does Massage Really Help Reduce Inflammation in Muscles? In Exercise 4.112 on page \(301,\) we learn that massage helps reduce levels of the inflammatory cytokine interleukin-6 in muscles when muscle tissue is tested 2.5 hours after massage. The results were significant at the \(5 \%\) level. However, the authors of the study actually performed 42 different tests: They tested for significance with 21 different compounds in muscles and at two different times (right after the massage and 2.5 hours after). (a) Given this new information, should we have less confidence in the one result described in the earlier exercise? Why? (b) Sixteen of the tests done by the authors involved measuring the effects of massage on muscle metabolites. None of these tests were significant. Do you think massage affects muscle metabolites? (c) Eight of the tests done by the authors (including the one described in the earlier exercise) involved measuring the effects of massage on inflammation in the muscle. Four of these tests were significant. Do you think it is safe to conclude that massage really does reduce inflammation?

Short answer

a) We should have less confidence, considering the issue of multiple comparisons. b) We cannot definitively state that a massage does not affect muscle metabolites, a lack of significant results doesn't confirm absence of an effect. c) It's plausible, given that half the tests showed significant results, but caution should be exercised, considering the possibility of false positives due to multiple testing.

Step-by-step solution

Understanding The Question (a)

This part of the exercise asks you to consider the possibility of getting a significant result due to chance because 42 tests were conducted. Therefore, statistical principles that measure the reliability of the data must be considered. The significant result could merely be a false positive.

Answer to The Question (a)

Yes, there should be less confidence in the result described in the earlier exercise. Although the result is statistically significant at the 5% level, because the authors performed 42 tests, there is a likelihood that some results will be statistically significant by pure chance. This is known as the problem of multiple comparisons.

Understanding The Question (b)

This segment of the exercise demands an understanding of the impact of non-significant results. The absence of a significant result doesn't necessarily mean no impact. It only demonstrates that the test wasn't robust enough to detect a difference.

Answer to The Question (b)

We can't definitively say that massage does not affect muscle metabolites based on the lack of significant results from the study. This is because non-significant results do not mean the absence of an effect, but only that the test did not detect a difference.

Understanding the Question (c)

It asks for an opinion based on the data provided. Four out of eight tests were significant, which could suggest that massage reduces inflammation, but there is still the issue of multiple testing.

Answer to The Question (c)

Considering that half of the tests carried out regarding inflammation showed significant results, it could be suggested that massage likely reduces inflammation. However, this conclusion should be made with caution, considering the issue of multiple testing where false positives could occur. Therefore, further studies should be carried out to further authenticate these results. A final conclusion can only be made when dates from multiple studies are consistent.