1. Correct. The answer is true.
(a) The sample mean `X and the modified sample variance are two such examples.
(b) The sample median and the sample statistic 1/2 (Q1+Q3), where Q1 and Q3 are the lower and the upper sample quartiles, are two such examples. Both statistics are unbiased estimates of the population mean, since the mean of their sampling distributions is the population mean. However, they are both inefficient compared of `X.
(c) The sample standard deviation S, the modified standard deviation , the mean deviation and the semi-interquartile range are four such examples.