3.7 Take-Home Points

• If a sample statistic is an unbiased estimator, we can use it as a point estimate for the value of the statistic in the population.

• A point estimate may come close to the population value but it is almost certainly not correct.

• A 95% confidence interval is an interval estimate of the population value. We are 95% confident that the population value lies within this interval. Note that confidence is not a probability!

• A larger sample or a lower confidence level yields a narrower, that is, a more precise confidence interval.

• A larger sample yields a smaller standard error, which yields a more precise confidence interval because the limits of a 95% confidence interval fall one standard error times the critical value below and above the value of the sample statistic.