Chapter 9

Question 1

unbiased characteristic

Answer 1

a stat whose mean value is equal to the value of the pop. characteristic being estimated (matches what you expect)

Question 2

in general, what statistic do you use to rep. the population and when do you use it?

Answer 2

the one with the SMALLEST standard deviation, when given a choice between several for estimating a pop. characteristic.

Question 3

important properties of t distribution (related to confidence intervals of population mean)

Answer 3

1. ) (corresponding to any fixed # of df) bell shaped
2. ) more spread out than standard normal (z) distribution
3. ) # of df increases, spread of “t” distrib decreases
4. ) # of df increases, corresponding sequence of “t” distrib approaches standard normal (z) distrib.
   * if not told confidence, assume 95%

Question 4

point estimate of population characteristic

Answer 4

a single # that is based on sample data and represents a plausible value of the characteristic