CHAPTER 5: Sampling and Surveys
Bell Work
You will be given the first 20 minutes or so to finish
the Unit A Assessment from Friday.
STATISTICS THROUGH APPLICATIONS/DAREN S. STARNES, DANIEL S. YATES, DAVID S. MOORE-2nd ed.
© 2011, 2005 by W. H. Freeman and Company
All rights reserved
CHAPTER 5: Sampling and Surveys
Bell Work
The Gallup Poll asked “What are you, personally, more
likely to do when you see a penny on the ground: leave it
on the ground and walk away or stop and pick it up?”
76% of respondents said that they would pick up the
penny. Sometimes what people say and what they do isn’t
the same, as the hand washing studies of Exercise 5.4
indicate.
Design an observational study to estimate the percent of
students at your school who would pick up a penny that is
left on the ground. (How could you ensure that your
sample is not biased?)
STATISTICS THROUGH APPLICATIONS/DAREN S. STARNES, DANIEL S. YATES, DAVID S. MOORE-2nd ed.
© 2011, 2005 by W. H. Freeman and Company
All rights reserved
CHAPTER 5: Sampling and Surveys
Vocabulary
The design of a statistical study is biased if it
systematically favors certain outcomes.
A voluntary response sample chooses itself by responding
to a general appeal. Write-in or call-in opinion polls
are examples of voluntary response samples.
Selection of whichever individuals are easiest to reach
is called convenience sampling.
Convenience samples and voluntary response samples are
often biased.
STATISTICS THROUGH APPLICATIONS/DAREN S. STARNES, DANIEL S. YATES, DAVID S. MOORE-2nd ed.
© 2011, 2005 by W. H. Freeman and Company
All rights reserved
CHAPTER 5: Sampling and Surveys
Simple Random Samples
A simple random sample (SRS) of size n consists of n
individuals from the population chosen in such a way that
every set of n individuals has an equal chance to be the
sample actually selected.
Ex. Drawing names from a hat
Choosing a sample by chance avoids bias by giving all
individuals an equal chance to be chosen.
STATISTICS THROUGH APPLICATIONS/DAREN S. STARNES, DANIEL S. YATES, DAVID S. MOORE-2nd ed.
© 2011, 2005 by W. H. Freeman and Company
All rights reserved
CHAPTER 5: Sampling and Surveys
Random Digits
A table of random digits is a long string of the digits
0,1,2,3,4,5,6,7,8,9 where
- Each entry in the table is equally likely to be any of
the 10 digits 0 through 9
- The entries are independent of each other
The randInt( function on the TI-84 also does this.
STATISTICS THROUGH APPLICATIONS/DAREN S. STARNES, DANIEL S. YATES, DAVID S. MOORE-2nd ed.
© 2011, 2005 by W. H. Freeman and Company
All rights reserved
CHAPTER 5: Sampling and Surveys
Example
You want to choose four member of the House of
Representative to panel. How can you create a SRS for
this scenario? Carry it out using both a graphing
calculator and Table B.
STATISTICS THROUGH APPLICATIONS/DAREN S. STARNES, DANIEL S. YATES, DAVID S. MOORE-2nd ed.
© 2011, 2005 by W. H. Freeman and Company
All rights reserved
CHAPTER 5: Sampling and Surveys
Example
You want to choose six of the 50 states. How can you
create a SRS for this scenario? Carry it out using both a
graphing calculator and Table B.
STATISTICS THROUGH APPLICATIONS/DAREN S. STARNES, DANIEL S. YATES, DAVID S. MOORE-2nd ed.
© 2011, 2005 by W. H. Freeman and Company
All rights reserved