You observe that the distribution of weights of individuals drawn from a random sample of the United States appears bimodal, there are peaks at 130 lbs. and 165 lbs. You were under the impression that weights follow a normal distribution. Why do you think this distribution differs so much?

A. The sample is not representative of the population.
B. Individuals weights better fit a uniform distribution
c. The standard dviation of weights is greater than the mean weight
D. The sample is comprised of males and females.
E. None of the above

Question

You observe that the distribution of weights of individuals drawn from a random sample of the United States appears bimodal, there are peaks at 130 lbs.  and 165 lbs.  You were under the impression that weights follow a normal distribution.  Why do you think this distribution differs so much?

A. The sample is not representative of the population. 
 B. Individuals weights better fit a uniform distribution
 c.  The standard dviation of weights is greater than the mean weight
 D. The sample is comprised of males and females. 
 E. None of the above

Mercury · Answer

Old question, answering to close

Nothing in the problem suggests that there was some sampling flaw. Furthermore, a standard deviation greater than the mean would not necessarily result in a bimodal distribution.

In this case, we look at the characteristics of the population. On average, men tend to weigh more than women, so in a mixed sample of men and women you would expect two modes (one for the men, one for the women)