1, An experiment is being designed to compare relief from hayfeversymptoms given anewdrug,

acommonlyuseddrug, and a placebo. Each subject who suffers from hayfever

and volunteers for the study is observed on three separatedays, with a different treatment used each day. There are two days betweentreatments, so that a treatment does not have acarry-over effect for the next treatment assigned.

a. What are the blocks in this blockdesign? What is this type of block designcalled?

b. What does it mean if the study is conducted as adouble-blind study?

c. How can randomization within the blocks be incorporated into thestudy?

2, During aone-week period a certain social media site conducted an experiment to research whether emotional states can be transferred to others via emotional contagion. Users were randomly selected to be part of two parallel studies in which the social media site manipulated the exposure to emotional expressions in theuser's news feed. Two parallel experiments were conducted. In onestudy, it reduced the positive emotionalcontent; in the otherstudy, the negative emotional content was reduced. For eachstudy, there was a control group(the users' news feed was notmanipulated), and an experimental group(the users' news feed was

manipulatedeither

positively ornegatively). Two variables were measured in each study after the manipulation by thesite: the percentage of all words produced by a person that was positive and the percentage of all words produced by a person that was negative. There were689,003 users in the study.

a. Explain why this study is an experiment.

b. Identity the experimental units.

c. For the study in which exposure tofriends' positive emotional content wasreduced, identity the explanatory variable and the two response variables.

d. The users randomly selected for the study were unaware they were part of this experiment. Provide a reason the site elected not to inform the selected users that they were part of an experiment. Provide a reason the users selected for the study may have felt not informing them about the study was unethical.

3,There have been anecdotal reports of the ability of hairspray to repel ticks. In one experimentconducted, 49 dogs were randomly assigned to receive either hairspray therapy or tickrepellent. After twomonths, the percentage successfully treated was 83% in the hairspray group and 55% in the tickrepellent group.

a. Identify the responsevariable, the explanatoryvariable, the experimentalunits, and the treatments.

b. Describe the steps of how assigning the 49

patients to the treatment groups could be randomized.

4,A certain journal presents a survey of opinions about fracking. Hydraulicfracturing, orfracking, is the process of drilling through rock and injecting a pressurized mixture ofsand, water, and chemicals that fractures the rock and releases oil and gas. There has been much debate in the media about its impact on theenvironment, on landowners, and on the economy. The survey involved contacting a nationally representative sample of 1960 adults from a large country in 2012. Of the 1960 people contacted, 1061 adults responded to the survey. The study reported that those more familiar with fracking, women, and those holding egalitarian worldviews were more likely to oppose fracking.

a. Describe the population of interest for this study.

b. Explain why a census is not practical for this study. What advantages does sampling offer?

c. Explain how nonresponse bias might be an issue in this study.

5, A club can select twomembers to attend a conference. Alloftheclubofficerswant to attend. There are total of four officers, and their designated positions within the club are President(P), Vice-president(V),Secretary(S),andTreasurer(T). For a simple random sample of two of the four officers who can attend theconference:

a. Show all the possible samples.

b. What is the chance that a particular sample of size 2 will be drawn?

c. What is the chance that the Secretary will be chosen?

6. More than75% of Americans answer yes whenasked, "Do you favor cracking down against illegal gunsales?" but more than75% say no whenasked, "Would you favor a law giving police the power to decide who may own afirearm?"

a. Which statistic would someone who opposes gun control prefer toquote?

b. Explain what is wrong with the wording of each of these statements.