16.
In research sponsored by Coca-Cola, 12,500 people were asked what contributes most to their
happiness, and 77% of the respondents said that it was their family or partner. Is this an example of
an observational study or a designed experiment?
(A)
Observational study because the researchers imposed a treatment
(B)
Observational study because the researchers did NOT impose a treatment
(C)
Designed experiment because the researchers imposed a treatment
(D)
Designed experiment because the researchers did NOT impose a treatment

17.
Which of the following statements about the interquartile range (IQR) are true?
I.
The IQR is zero only when all of the observations in the data set are the same value.
II.
The IQR represents the range of the middle 50% of observations in a data set.
III.
The IQR is affected by outliers in a distribution.

18.
Sandy has an average bowling score of 180 and bowls in a league where the average for all bowlers
is 150 and the standard deviation is 20. Chantel has an average bowling score of 190 and bowls in a
league where the average is 160 and the standard deviation is 15. Who is the better bowler relative to
the rest of her league, Sandy or Chantel?

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STAT 2300
Test #1
Summer II 2018
19.
The director of a fitness center wants to examine the effects of two exercise classes (spinning and
aerobics) on body fat percentage. A six-week spinning class and a six-week aerobics class are
offered at the same time and on the same days, so that a person can enroll in only one of them. A
new class of each is about to begin, and each class has 25 people in it. Ten people are randomly
selected from each class. Each person's body fat percentage is measured at the beginning and again
at the end of the six-week class. Using the change in body fat percentage as the response variable,
the director determines that there is a statistically significant difference between the treatment
means. Which of the following is a lurking variable in this study?

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