Question

The paper "Effects of Caffeine on Repeated Sprint Ability, Reactive Agility Time, Sleep and Next Day Performance" (Journal of Sports Medicine and Physical Fitness \([2010]: 455-464)\) describes an experiment in which male athlete volunteers who were considered low caffeine consumers were assigned at random to one of two experimental groups. Those assigned to the caffeine group drank a beverage which contained caffeine one hour before an exercise session. Those in the no-caffeine group drank a beverage that did not contain caffeine. During the exercise session, each participant performed a test that measured reactive agility. The researchers reported that there was no significant difference in mean reactive agility for the two experimental groups. In the context of this experiment, explain what it means to say that there is no significant difference in the group means.

Short answer

In this context, saying there is 'no significant difference' in group means suggests that according to the statistical tests used, there is no sufficient evidence to claim that caffeine has a statistically significant effect on the reactive agility of male athletes who are low caffeine consumers. Therefore, any observed differences could be down to random variation rather than the effect of caffeine.

Step-by-step solution

Understanding the Experiment

Firstly, it's crucial to understand the experimental setup. Male athletes who were low caffeine consumers were randomly assigned to either a caffeine group or a non-caffeine group. The caffeine group consumed a caffeinated drink an hour before exercise, while the non-caffeine group consumed a non-caffeinated drink. The participants then performed a test measuring reactive agility.

Defining 'No Significant Difference'

The researchers declared there was 'no significant difference' between the group means. This doesn't mean the means were exactly the same. It simply connotes that, according to the statistical tests employed, there is not satisfactory evidence to assert that the means of the two groups are different within the context of statistical significance.

Interpreting 'No Significant Difference'

In the context of this experiment, it could mean that the addition of caffeine does not impact, to a statistically significant degree, the reactive agility of low caffeine consuming male athletes. The results suggest that the effects due to caffeine consumption observed in the experiment (if any) could be due to chance variation rather than a true effect of caffeine.