**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 (Q_{1}+Q_{3}), where
Q_{1} and Q_{3} 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.