Unit III Questions
101. A proud legislator claims that your state’s new law against talking on a cell phone while
driving has reduced cell phone use to less than 12% of all drivers. While waiting for your bus
the next morning, you notice that 4 of the 10 people who drive by are using their cell phones.
Does this cast doubt on the legislator’s figure of 12%? Use a simulation to estimate the
likelihood of seeing at least 4 of 10 randomly selected drivers talking on their cell phones if the
actual rate of usage is 12%. Explain your conclusion clearly.(Use the random number table
provided for your simulation.)
Unit III Questions
101. A proud legislator claims that your state’s new law against talking on a cell phone while
driving has reduced cell phone use to less than 12% of all drivers. While waiting for your bus
the next morning, you notice that 4 of the 10 people who drive by are using their cell phones.
Does this cast doubt on the legislator’s figure of 12%? Use a simulation to estimate the
likelihood of seeing at least 4 of 10 randomly selected drivers talking on their cell phones if the
actual rate of usage is 12%. Explain your conclusion clearly.(Use the random number table
provided for your simulation.)
Component is check one car with the outcomes of:
01-12 on cell phone
Red
13-99,00 not on cell phone
–
Check ten cars checking for:
Four or more on cell phone
Y
Not 4 or more on cell phone
N
TABLE OF RANDOM NUMBERS
39634 62349 74088 65564 16379 19713 39153 69459 17986 24537
14595 35050 40469 27478 44526 67331 93365 54526 22356 93208
30734 71571 83722 79712 25775 65178 07763 82928 31131 30196
64628 89126 91254 24090 25752 03091 39411 73146 06089 15630
Unit III Questions
101. A proud legislator claims that your state’s new law against talking on a cell phone while
driving has reduced cell phone use to less than 12% of all drivers. While waiting for your bus
the next morning, you notice that 4 of the 10 people who drive by are using their cell phones.
Does this cast doubt on the legislator’s figure of 12%? Use a simulation to estimate the
likelihood of seeing at least 4 of 10 randomly selected drivers talking on their cell phones if the
actual rate of usage is 12%. Explain your conclusion clearly.(Use the random number table
provided for your simulation.)
During my simulation of 20 trials, I found that I shouldn’t see four or
more out of ten drivers if the true proportion is only 12% of drivers
are on the cell phone. Therefore, based on what I saw, I suspect that
the claim of 12% is too low.
Unit III Questions
104. Researchers at the Washington University School of Medicine randomly placed 480 rats
into one of three chambers containing radio antennas. One group was exposed to digital cell
phone radio waves, the second to analog cell phone waves, and the third group to no radio
waves. Two years later the rats were examined for signs of brain tumors. In June 2002 the
scientists said that differences among the three groups were not statistically significant.
a) Is this a study or an experiment? Explain.
Unit III Questions
104.. Researchers at the Washington University School of Medicine randomly placed 480 rats
into one of three chambers containing radio antennas. One group was exposed to digital cell
phone radio waves, the second to analog cell phone waves, and the third group to no radio
waves. Two years later the rats were examined for signs of brain tumors. In June 2002 the
scientists said that differences among the three groups were not statistically significant.
b) Explain in this context what “statistically significant” means.
Unit III Questions
102. Researchers at the Washington University School of Medicine randomly placed 480 rats
into one of three chambers containing radio antennas. One group was exposed to digital cell
phone radio waves, the second to analog cell phone waves, and the third group to no radio
waves. Two years later the rats were examined for signs of brain tumors. In June 2002 the
scientists said that differences among the three groups were not statistically significant.
c) Comment on the fact that this research was supported by funding from Motorola,
a manufacturer of cell phones.
Unit III Questions
15. An experiment to test a new laundry detergent, SparkleKleen, is being conducted by a
consumer advocate group. They would like to compare its performance with that of a
laboratory standard detergent they have used in previous experiments. They can stain 16
swatches of cloth with 2 tsp. of a common staining compound and then use a well-calibrated
optical scanner to detect the amount of the stain that is left after washing with detergent. To
save time in the experiment, several suggestions have been made. Comment on the possible
merits and drawbacks of each one.
a) Since data for the laboratory standard detergent are already available from previous
experiments, for this experiment wash all 16 swatches with SparkleKleen, and compare the
results with the previous data.
Unit III Questions
105. An experiment to test a new laundry detergent, SparkleKleen, is being conducted by a
consumer advocate group. They would like to compare its performance with that of a
laboratory standard detergent they have used in previous experiments. They can stain 16
swatches of cloth with 2 tsp. of a common staining compound and then use a well-calibrated
optical scanner to detect the amount of the stain that is left after washing with detergent. To
save time in the experiment, several suggestions have been made. Comment on the possible
merits and drawbacks of each one.
b) Use both detergents with eight separate runs each, but to save time, use only a 10-second
wash time with very hot water.
Unit III Questions
105. An experiment to test a new laundry detergent, SparkleKleen, is being conducted by a
consumer advocate group. They would like to compare its performance with that of a
laboratory standard detergent they have used in previous experiments. They can stain 16
swatches of cloth with 2 tsp. of a common staining compound and then use a well-calibrated
optical scanner to detect the amount of the stain that is left after washing with detergent. To
save time in the experiment, several suggestions have been made. Comment on the possible
merits and drawbacks of each one.
c) To ease bookkeeping, run successively all of the standard detergent washes on eight
swatches, then run all of the SparkleKleen washes on the other eight swatches.
Unit III Questions
105. An experiment to test a new laundry detergent, SparkleKleen, is being conducted by a
consumer advocate group. They would like to compare its performance with that of a
laboratory standard detergent they have used in previous experiments. They can stain 16
swatches of cloth with 2 tsp. of a common staining compound and then use a well-calibrated
optical scanner to detect the amount of the stain that is left after washing with detergent. To
save time in the experiment, several suggestions have been made. Comment on the possible
merits and drawbacks of each one.
d) Rather than run the experiment, use data from the company that produced SparkleKleen,
and compare them with past data from the standard detergent.
Unit III Questions
106. Political analyst Michael Barone has written that “conservatives are more likely than
others to refuse to respond to polls, particularly those polls taken by media outlets that
conservatives consider biased” (The Weekly Standard, March 10, 1997). The Pew Research
Foundation tested this assertion by asking the same questions in a national survey run by
standard methods and in a more rigorous survey that was a true SRS with careful follow-up to
encourage participation. The response rate in the “standard survey” was 42%. The response
rate in the “rigorous survey” was 71%.
a) What kind of bias does Barone claim may exist in polls?
Unit III Questions
106. Political analyst Michael Barone has written that “conservatives are more likely than
others to refuse to respond to polls, particularly those polls taken by media outlets that
conservatives consider biased” (The Weekly Standard, March 10, 1997). The Pew Research
Foundation tested this assertion by asking the same questions in a national survey run by
standard methods and in a more rigorous survey that was a true SRS with careful follow-up to
encourage participation. The response rate in the “standard survey” was 42%. The response
rate in the “rigorous survey” was 71%.
b) What is the population for these surveys?
Unit III Questions
106. Political analyst Michael Barone has written that “conservatives are more likely than
others to refuse to respond to polls, particularly those polls taken by media outlets that
conservatives consider biased” (The Weekly Standard, March 10, 1997). The Pew Research
Foundation tested this assertion by asking the same questions in a national survey run by
standard methods and in a more rigorous survey that was a true SRS with careful follow-up to
encourage participation. The response rate in the “standard survey” was 42%. The response
rate in the “rigorous survey” was 71%.
c) On the questions of political position, the Pew researchers report the following table:
Conservative
Moderate
Liberal
Standard Survey
37%
40%
19%
Rigorous Survey
35%
41%
20%
What makes you think these results are incomplete?
Unit III Questions
106. Political analyst Michael Barone has written that “conservatives are more likely than
others to refuse to respond to polls, particularly those polls taken by media outlets that
conservatives consider biased” (The Weekly Standard, March 10, 1997). The Pew Research
Foundation tested this assertion by asking the same questions in a national survey run by
standard methods and in a more rigorous survey that was a true SRS with careful follow-up to
encourage participation. The response rate in the “standard survey” was 42%. The response
rate in the “rigorous survey” was 71%.
d) The Pew researchers report that differences between opinions expressed on the two surveys
were not statistically significant. Explain what “statistically significant” means in this context.