Why aren't voluntary response samples usually representative of the population

a: the people who volunteer will be the only ones you are not represented

b: the people who don't volunteer will be the only ones that are represented

c: the people who volunteer usually have a motive to do so and will be the only ones represented

d: the people who don't volunteer probably have really strong opinions of the subject

Need now max recorded the heights of 500 male humans. he found that the heights were normally distributed around a mean of 177 centimeters. which statements about max’s data must be true? a) the median of max’s data is 250 b) more than half of the data points max recorded were 177 centimeters. c) a data point chosen at random is as likely to be above the mean as it is to be below the mean. d) every height within three standard deviations of the mean is equally likely to be chosen if a data point is selected at random.