Which of the following statements is not correct? (a) in a proper random sampling, every element of the population has a known (and often equal) chance of being selected. (b) the precision of a sample mean or sample proportion depends only upon the sample size (and not the population size) in a proper random sample. (c) convenience sampling often leads to biases in estimates because the sample is often not representative of the population. (d) if a sample of 1,000,000 families is randomly selected from all of canada (with about 8,000,000 families) and the average family income is computed, then the true value of the family income for all families in canada is known. (e) the sampling distribution of the sample mean describes how the sample mean will vary among repeated samples.