Exam 9: Estimation Using a Single Sample

All else being equal, the higher the confidence level, the wider the confidence interval.

An understanding of bird's choices of habitat is a crucial element in understanding avian biology and ecology.One aspect of habitat choice is the pattern of their

Eyestrain is thought to be associated with different types of office work.The Acme Temp-Help Company provides short-term employees to substitute for vacationing data entry personnel.Previous research has shown that approximately 21% of full time data entry personnel have eyestrain, and Acme would like to estimate the proportion, p , of their 6,000 part-time data entry employees that have eyestrain. a)They would like to estimate p to within 0.05 with 95% confidence.If they accept the starting value of 0.21 as a reasonable initial estimate of p , what sample size should they use for their study? b)Suppose Acme had felt that the working conditions of their temporary data entry personnel were different enough that they should not depend on the 0.21 as an initial estimate.In a few sentences, explain how your procedure for choosing a samples size would differ from your solution in part (a).(Do NOT recalculate a new estimate of the necessary sample size!)

A recent study investigated the effects of a "Buckle Up Your Toddlers" campaign to get parents to use the grocery cart seat belts.Investigators observed a simple random sample of parents in a large city, and found 192 out of 594 parents buckling up their toddlers. a)Compute a point estimate of the true proportion of all parents who buckle up their toddlers. b)Construct and interpret a 95% confidence interval for p , the true proportion of all parents who buckle up their toddlers.

If the distribution of a population is symmetric, both the mean and median give unbiased estimates of the population mean.What criteria would you consider in choosing which statistic to use if you wanted to estimate the population mean?

Using an unbiased statistic guarantees that there will be no systematic tendency to under- or overestimate the value of the population characteristic and that estimates will almost always be relatively close to the true value.

In a couple sentences, define a "point estimate" and "interval estimate" of a population characteristic.What is the difference between the two?

What is the difference between an unbiased statistic and a biased statistic?

In a study of termite populations in Swaziland, the following data were gathered on the percentage of termites that were classified as "major workers" at eight randomly selected sites: a)Use the given data to produce a point estimate of m, the true mean percentage of termites that are "major workers." b)Use the given data to produce an unbiased point estimate of , the population variance of the percentage of termites that are "major workers."

A t curve is bell-shaped like the z curve but is less spread out.

Bicycle crashes are a common cause of severe injuries in childhood.A researcher theorized that this might be because of inadequate "gap" time (the time between a bicycling child clearing an intersection and the subsequent entry of an oncoming car into that intersection).A researcher experimentally investigated the gap judgments of 10-year-olds by placing them in a computer-generated virtual environment of cars approaching an intersection at 25 mph.The following gap times were observed for ten randomly selected children: a)Use the given data to produce a point estimate ofm, the population mean gap time of 10-year-olds from this population. b)Use the given data to produce an unbiased point estimate of , the population variance of the gap time of 10-year-olds from this population.

In a couple sentences, define a "point estimate" and "interval estimate" of a population characteristic.What is the difference between the two?