Module 1 – Statway College
Please answer all of the questions below. Show your work. Please reach out to me if you have any
questions.
1. What is the difference between an observational study and an experiment?
2. In October 2018 through December 2018, the Centre for Social Development in Africa surveyed 3,431
South African adults on their voting preferences and primary reasons for voting. The study found that in
adults aged 18 – 34, 66.7% voted ANC; in adults aged 35 – 60, 70.2% voted ANC; and in adults older
than 60, 73.1% voted ANC. The study also found that out of all voters, 27% said that their voting
preferences were based primarily on concerns about democratic rights, while 58% said their voting
preferences were based primarily on concerns about their socio-economic well-being.
(a) What is the population of interest in this survey?
(b) What variables did this survey measure?
(c) Can we conclude that a person’s age causes them to vote a certain way?
3. A study examined the impact of taking aspirin on blood pressure levels for individuals diagnosed with
pre-hypertension – slightly higher than normal blood pressure. 244 adults with pre-hypertension
participated in the study. Participants were randomly assigned to three groups: (1) a group instructed to
only continue their diet and hygiene regiments, (2) a group instructed to continue their diet and hygiene
regiments and take a 100 mg aspirin tablet daily before bedtime, and (3) a group instructed to continue
their diet and hygiene regiments and take a 100 mg aspirin tablet daily in the morning. The study was
conducted over a three-month period. It found that the daily use of aspirin before bedtime lead to a
reduction in blood pressure, whereas the other two treatments lead to no change in blood pressure levels.
(a) What is the population of interest in this experiment?
(b) What is the explanatory variable? What values are assigned to the explanatory variable?
(c) What is the response variable?
(d) Identify the control group in this experiment.
(e) What are some potential confounding variables in this experiment?
(f) Is a cause-and-effect conclusion appropriate for this study? Explain.
4. The data set below contains the maximum wind speeds (in miles per hour) of 15 hurricanes in 2005
hurricane season.
[75, 150, 160, 105, 175, 115, 90, 85, 80, 180, 80, 75, 185, 115, 85]
(a) Find the mean maximum wind speed of these hurricanes.
(b) Determine the 5-number summary of the data.
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(c) Create a boxplot of the data.
(d) Determine the interquartile range.
(e) Are there any outliers? Explain.
(f) Which measure, mean or median, best describes the typical maximum wind speed in this sample?
5. The dotplot below summarizes life-expectancy data for 188 countries. Each dot details a country’s
average life expectancy for the year 2015. For example, the 2015 average life expectancy for the United
States is 79 years. This means that the average person born in the United States in 2015 is predicted to
live for 79 years.
Describe the center, shape, and spread of this distribution.
6. The stacked dotplot compares life expectancies from a random sample of 5 countries from Asia and a
random sample of 5 countries in Africa from 2015.
(a) Which sample has a larger mean?
(b) Which sample has a larger standard deviation?
(c) The table below contains the typical life expectancies of the five counties in Africa in 2015. Find
and interpret the standard deviation of this sample.
(d) Which country in the sample has the greatest impact on the sample standard deviation?
Country
Life Expectancy
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Algeria
Djibouti
Kenya
Senegal
Swaziland
Zambia
76.5
64.6
66.6
66.1
51.5
59.0
7. A new car-buying guide reported on the number of seconds required for a variety of cars to accelerate
from 0 to 30 mph. The cars were also classified into four categories according to their type. The
following box plots display the distribution of acceleration times for each type of car.
(a) Which type of car has the greatest median acceleration time? Estimate the median.
(b) Which type of car has acceleration times with the smallest interquartile range (IQR)? Estimate the
IQR.
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