You just saw a commercial for the Tread Master, an exercise machine that claims an average weight loss of 10 pounds. A commercial for the Climber, a competing product, claims that only 1 out of 10 users of the Tread Master lost any weight at all. The rest of them gained weight. How can both of these claims be true?

Answer:

Both claims can be true

Explanation:

This is possible by using a biased sampling technique. In other words, if the sampler is targeted to a specific audience in order to achieve a specific outcome that could lead to such a situation. Both companies may have been able to use different samples of different sizes by serving different user groups. The Tread-master may have been able to sample active users exercising daily or accurately because they tend to lose weight quickly. Climbers can extract a sample of inactive users for users who generally do not exercise accurately or do not exercise on a daily basis. Therefore, due to incorrect, biased, or different sample selection, the two claims go in opposite directions.

This scenario can have so many different possibilities for statistics that both commercials use and can both be true. Time is an important factor to consider in weight loss, both of these commercials can be true if using different timeframes for measuring weight loss. If one is measuring the weight loss of its users within the first week the results will not be the same as if the other is using the first month to determine weight loss. In the first week, users can be motivated and workout harder and more consistently than in the third week.

Another factor to consider is body fat vs. muscle. Muscle weighs more than fat so if the users are measured just by weight loss then the numbers will not reflect the results properly. For example, users who have lost fat in the first week might be at the point where they are building muscle by the third week showing that they have gained weight, which is true, but it is muscle instead of fat.

Without having all of the data it is too hard to tell which commercials are using statistics that actually matter versus statistics that will make people buy. Numbers are an eye catcher so seeing claims such as "participants all lost ten pounds in the first week" is going to make a big impact because of the health kick everyone wants to lose weight. Doing a bit of additional research into products and claims is always necessary so that you can be a knowledgeable buyer.