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

Answer 1

if we pooled together men and women and made a frequency distribution of heights, you would see that the frequency spikes around the mean height of women and the mean height of men.

Answer 2

oh so the sample is comprised of males and females

Answer 3

The same goes if you were to pool together first graders and tenth graders, and measure their height. you would end up with a bimodal graph (actually a 4 modal graph due to the respective genders).

Answer 4

oh ok, would that mean that it isn't representative of the population because the numbers differ so much and it would be a normal distribution if they didn't differ?

Answer 5

so a) is correct

Answer 6

ok thanks(:

Answer 7

it is respresentative of the population, but it depends on what population you are talking about

Answer 8

american male adult heights are normally distributed.
american female adult heights are normally distributed.
but american heights of men and women pooled together,
that is not normally distributed.

Answer 9

oh ok thanks!

Answer 10

the surveyor was just confused because they expected the weights to be normally distributed. but on closer inspection it was found to be bimodal .
That may imply the underlying population is not homogenous (similar in every respect), namely there are different genders.

Answer 11

ok thanks