Solve all parts.

1) A probability sample is a a. type of voluntary response sample.

b. type of census. c. type of convenience sample.

d. sample that is chosen by chance.

2) While an analyst considers the time plot of the closing value of the Dow Jones Industrial Average, he notices a trend. This means he sees

a. a persistent long-term rise or fall. b. changes due to nonresponse. c. changes due to confounding. d. a pattern in a time series that repeats itself at known regular intervals of time. e. the margin of error

3) Does the herb Echinacea help the common cold? A study by researchers at the University of Wisconsin-Madison published a study in the Annals of Internal Medicine that found that Echinacea was no better than a placebo. The researchers randomly assigned 142 college students who recently came down with colds to receive either Echinacea in capsule form or a placebo in capsule form. The students did not know if they were getting the herb or the placebo and took their treatment for 10 days. The researchers reported that there was no statistically significant difference in the duration of the cold between these groups.

The no statistically significant difference in the results means

a. the study was designed poorly. b. the study has no practical importance.

c. the difference in duration of colds between the Echinacea and placebo groups was large enough that it would rarely occur by random chance.

d. the difference in duration of colds between the Echinacea and placebo groups was small enough to explain by random chance.