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Lecture 3

STAT 101 Lecture Notes - Lecture 3: Pew Research Center, Root Mean Square, Scatter Plot


Department
Statistics
Course Code
STAT 101
Professor
Stephenson Robert
Lecture
3

Page:
of 5
1
Stat 104 Homework 3 Name:____________________
Due Tuesday, February 9, 2016
Reading: January 22 February 5 Chapter 3
February 10 February 18 Chapter 4
Practice (do not hand in):
The following questions from the text have the answers provided in the back of the book. They
are not to be handed in! They may help you when answering the questions for the assignment.
Questions 3.1, 3.5, 3.11, 3.21
Assignment (hand in):
1. Complete the following problems from the text:
The answers to odd numbered problems are in the back of the text. If you have a
question about the answers to the problems in the text, please see your course
instructor.
3.9 Gender gap in party ID (excluding part d)
3.15 Internet use correlations (excluding part c)
2. For this question, you will continue to work with the example you used in homework
assignment 2, however a new JMP file is on Blackboard. Recall: The Pew Research Center
conducted a survey of a random sample of U.S. adults in August 15-25, 2014. One question
that the adults were asked was “Which of these is a major concern about the overuse of
antibiotics?” Their response options were: 1. It can lead to antibiotic-resistant bacteria, 2.
Antibiotics are very expensive, or 3. People will become addicted to antibiotics.1 Option 1
was the correct answer. A handful of adults volunteered an answer or “Don’t know” and
some refused to answer.
An additional variable has been added to the JMP file that is posted on Blackboard for
homework assignment 3, “Is one or more of your degrees in a scientific field, or not?
a) Which variable is the explanatory variable and which is the response variable? Explain.
The explanatory variable is whether or not your degree is in a scientific field and the
response variable is the concern about overuse of antibiotics variable because we
would like to see if whether or not adults have a scientific degree helps explain
understanding of the concern about overuse of antibiotics.
1 http://www.pewinternet.org/2015/10/22/science-and-religion/
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2
b) Create a table to display the relationship between Concern about the overuse of
antibiotics? and Degree in Scientific Field?. Attach a copy of your table to the end of
your assignment.
Contingency Table
Degree in Scientific Field? By Concern about the overuse of antibiotics?
Count
Total %
Col %
Row %
It can lead to
antibiotic-
resistant
bacteria
Antibiotics
are very
expensive
People will
become
addicted to
antibiotics
(VOL.) Don't
know
(VOL.)
Refused
Total
Yes
264
32.63
37.08
88.00
14
1.73
46.67
4.67
17
2.10
31.48
5.67
2
0.25
22.22
0.67
3
0.37
75.00
1.00
300
37.08
No
448
55.38
62.92
88.02
16
1.98
53.33
3.14
37
4.57
68.52
7.27
7
0.87
77.78
1.38
1
0.12
25.00
0.20
509
62.92
Total
712
88.01
30
3.71
54
6.67
9
1.11
4
0.49
809
c) What percent of these adults said they had a degree in a scientific field? Note that you
should always keep at least 2 decimal places in your answers for any assignment in this
class.
37.08%
d) What percent of adults with a degree in a scientific field said a major concern is it can
lead to antibiotic-resistant bacteria?
88.00%
e) What percent of adults without a degree in a scientific field said a major concern is it can
lead to antibiotic-resistant bacteria?
88.02%
f) Using appropriate statistics (relevant percentages in the table), is there a relationship
between Concern about the overuse of antibiotics? and Degree in Scientific Field?
Explain.
No, there does not appear to be a relationship between Concern about the overuse of
antibiotics? and Degree in Scientific Field. The percent that chose each response to
the question about antibiotics was similar for adults that had degrees in scientific
fields and those that did not. For example, 88.00% of adults with scientific degrees
said it can lead to antibiotic-resistant bacteria, which is almost identical to adults
that did not have scientific degrees, 88.02%.
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3
3. For this question, you will continue to work with the dataset you used in homework
assignment 2. Recall: The World Bank collects data from countries around the world. The
AllCountries dataset2 for this assignment is posted on BlackBoard. The dataset includes
characteristics of 213 countries in 2008 and there are multiple variables. In this assignment,
you will examine the following variables: Rural and Cell. Rural refers to the percentage of
the population living in rural areas. Cell refers to cell phone subscriptions per 100 people.
Suppose we are interested in using rural area percentage to predict cell phone use.
a) Which variable is the explanatory variable and which is the response variable? Explain.
Rural area percentage is the explanatory variable and cell phone subscriptions is the
response variable because we are interested in predicting/explaining cell phone
subscriptions using rural area percentage.
b) Create a scatterplot. Attach a copy of your graph to the end of your assignment.
Multivariate
Correlations
Rural
Cell
Rural
1.0000
-0.5375
Cell
-0.5375
1.0000
There are 12 missing values. The correlations are estimated by REML method.
Scatterplot Matrix
c) Describe the general relationship between the percentage of the population living in rural
areas and cell phone subscriptions using the scatterplot.
2 http://finzi.psych.upenn.edu/library/Lock5withR/html/AllCountries.html
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