1.2 sampling from a population

To determine the height distribution of female high school students, the rosters are collected from 20 randomly selected high school girls basketball teams. a)The sample (b)The population of interest (c)A population we can generalize to given the sample

(a)Girls on the selected basketball teams (b)All female high school students (c)Female HS students on a basketball team

To estimate the average number of tweets from all twitter accounts in 2015, one of the authors randomly selected 10 of his followers and counted their tweets. (a)The sample (b)The population of interest (c)A population we can generalize to given the sample

(a)The 10 selected twitter accounts (b)All twitter accounts (c)The author's followers' twitter accounts

In Data 1.4, we describe the results of a question asked by a national newspaper columnist: "If you had it to do over again, would you have children?" In addition to those results and a followup national survey, the Kansas City Star selected a random sample of parents from Kansas City and asked them the same question. In this sample, 94% said "Yes." To what population can this statistic be generalized?

Because this was a random sample of parents in Kansas City, the result can be generalized to all parents in Kansas City.

Take 10 apples off the top of a truckload of apples and measure the amount of bruising on those apples to estimate how much bruising there is, on average, in the whole truckload.

From the description, it appears that this method of data collection is not biased.

The population is adults between the ages of 18 and 22. A sample of 100 students is collected from a local university, and each student at the university had an equal chance of being selected for the sample.

No, this is not a random sample, because certain segments of the population (e.g. those not attending college) cannot be selected.

A subscription-based music website tracks its total number of active users.

Population

A questionnaire to understand athletic participation on a college campus is emailed to 50 college students, and all of them respond.

Sample

Five hundred Canadian adults are asked if they are proficient on a musical instrument.

Sample: 500 Canadian adults; Population: All Canadian adults

The Nielsen Corporation attaches databoxes to televisions in 1000 households throughout the US to monitor what shows are being watched and produce the Nielsen Ratings for television

Sample: The 1000 households Population: All US households with TV

During the Second World War, the U.S. military collected data on bullet holes found in B-24 bombers that returned from flight missions. The data showed that most bullet holes were found in the wings and tail of the aircraft. Therefore, the military reasoned that more armor should be added to these regions, as they are more likely to be shot. Abraham Wold, a famous statistician of the era, is reported to have argued against this reasoning. In fact, he argued that based on these data more armor should be added to the center of the plane, and NOT the wings and tail. What was Wald's argument?

The sample of planes that return from bombing missions was biased. More bullet holes were found in the wings and tail because planes that were shot in other regions were more likely to crash and not return.

Ask a random sample of people in a given school district, "Excellent teachers are essential to the well-being of children in this community, and teachers truly deserve a salary raise this year. Do you agree?" Use the results to estimate the proportion of all people in the school district who support giving teachers a raise.

This is biased because the way the question is worded is not at all objective. Although the sample is a random sample, the wording bias may distort the results.

The population is the approximately 25,000 protein-coding genes in human DNA. Each gene is assigned a number (from 1 to 25,000), and computer software is used to randomly select 100 of these numbers yielding a sample of 100 genes.

Yes

In a random sample of 3500 Canadian consumers, about 71% report that they regularly stream music.26 (a) Is the sample likely to be representative of all Canadian consumers? Why or why not? (b) Is it reasonable to generalize this result and estimate that about 71% of all Canadian consumers regularly stream music?

a.) Yes, the sample is likely to be representative since it is a random sample. b.) Yes, since the sample is a random sample, we can generalize to the population of all Canadian consumers.