5.35 Cholesterol levels of teenagers. A study of the health of teenagers plans to measure the blood cholesterol level of an SRS of 13- to 16-year olds. The researchers will report the mean from their sample as an estimate of the mean cholesterol level μ in this population.

1. (a) Explain to someone who knows no statistics what it means to say that is an “unbiased” estimator of μ.

2. (b) The sample result is an unbiased estimator of the population truth μ no matter what size SRS the study chooses. Explain to someone who knows no statistics why a large sample gives more trustworthy results than a small sample.