LOOKING AT SOME BASICS Can you tell the difference?

ELVIS On the twelfth anniversary of the death of Elvis Pressley, a Dallas Record company sponsored a national call-in survey. Listeners of over 1000 radio stations were asked to call a number (at a charge of $2.50) To voice their opinion concerning whether or not Elvis was really dead. It turned out that 56% of the callers felt that Elvis was alive. Identify the population of interest and the sample actually used to study the population. Do you think that 56% is an accurate reflection of beliefs of all Americans on this issue? If not, identify some of the flaws in the sampling method.

ELECTION In 1936, Literary Digest magazine conducted the most extensive (to that date) public opinion poll in history. They mailed out questionnaires to over 10 million people whose names and addresses they had obtained from telephone books and vehicle registration lists. More than 2.4 million people responded, with 57% indicating they would vote for Republican Alf Landon in the upcoming Presidential election. (Incumbent Democrat Franklin Roosevelt won the election, carrying 63% fo the popular vote.) Identify the population of interest and the sample actually used. Offer an explanation as to how Literary Digest’s prediction could have been so much in error. In particular, comment on why its sampling method made it Vulnerable to overestimating support for the Republican candidate.

PARAMETER OR STATISTIC? * The 56% of callers who believed that Elvis was alive. * The 57% of voters who indicated they would vote for Alf Landon. * The 63% of voters that voted for Franklin Roosevelt. * The mean years of service among the 100 Senators. * The mean years of service among 5 randomly chosen Senators. * The proportion of men in the 2011 Senate.

YOU DO THE SRS You must chose 6 people to go on a dangerous mission to Coach Moretz’s office. Your conscious won’t let you just pick 6 people so you decide to use an SRS to make the choice. Choose from the following: AllieSebastian TaylorEmily Ben GracieChris TateShelby Robert JakeOlivia AbbyEan Evan Devise at least 3 methods to take the SRS. Write your directions clearly so someone else could read them and carry it out.

4 TYPES OF STUDIES Anecdotes: With which the investigator merely recounts instances known to him or her. Surveys: with which the investigator asks people to answer questions about their opinions or practices. Observational studies: the investigator passively observes and records information on observational units, such as people’s practices. Experiments: the investigator deliberately imposes some condition on the subjects or experimental units, observing and recording results.

AN APPLE A DAY Suppose you want to collect data to study whether the expression “an apple a day keeps the doctor away” has any validity. In other words, you want to investigate whether eating apples has any health benefit. Consider 4 different designs: (i)You take a random sample of individuals, identify which do and do not eat apples regularly, and then follow them for 6 months to see who requires a visit to a doctor and who does not. (ii)You take a random sample of physicians and ask them whether they have noticed any health benefits of eating apples.

AN APPLE A DAY (iii)You take a random sample of individuals, randomly assign half to eat an apple a day for the next 6 months and the other half not to, and then see who requires a visit to the doctor and who does not. (iv)You recall that your Uncle Buck loved apples and was never sick a day in his life, while your Uncle Fester despised apples and was often ill.

OUTLINE AN EXPERIMENT With the design that described an experiment, outline the design. Label the design clearly. You take a random sample of individuals, randomly assign half to eat an apple a day for the next 6 months and the other half not to, and then see who requires a visit to the doctor and who does not.