CHAPTER 3

DESIGNING STUDIES AND COLLECTING DATA

3-2.

The effect of Pepsi over Coke is $$\frac{4+3+5+4+2}{5} - \frac{3+2+1+3}{4} = 3.6-2.25 = 1.35$$

3-6.

Yes it is a controlled experiment since treatments (old, new) are assigned to experimental units (subjects) and a response (removal of clots) observed.

3-7.

Blocking:paint each boat with both paints. This will reduce regional/environmental differences.

3-9.

a.

Response bias; results in undercount; interview separately.

b.

Nonresponse bias and response bias results in undercount; It is hard to find and get responses from people who don't want to be found.

c.

Selection bias; results in overrepresentation of extreme views;Get a frame and select a real sample instead of letting the sample select itself.

3-19.

As parties come in, randomly assign them to a server and to receive a smiley face or ``no smiley face". Replicate with a number of parties and servers. Compare tip percents at the end. Could also block by type or size or composition of party, etc.

3-20.

The experimenter could have blocked by kind of worker and assigned full time workers to both types of incentive schemes and part time workers to both types of incentive schemes.

3-24.

a.

Yes it was a controlled experiment since treatments (aspirin/placebo) were assigned to experimental units (mice) and a response (death/not) observed.

b.

Not necessarily. It may be due to the drug.

3-33.

Blocking:Give each individual both sodas.
Randomization:Randomize order (can also be blocked.)
Replication:Use a large number of subjects to get precise conclusions.