STAT 1450 Lecture 8: Chapter 08 Notes - Producing Data Sampling
17 Sep 2020
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Chapter 8, page 1
STAT 1450 COURSE NOTES – CHAPTER 8
PRODUCING DATA: SAMPLING
Connecting Chapter 8 to our Current Knowledge of Statistics:
Part I of the text emphasized ways of organizing, analyzing, and even interpreting data.
N, ell fc methodologies associated with collecting data.
Situation:
State Farm & Allstate have been mainstays as the Two Largest Auto Insurers in the
c. Ge h a cah he a. GEICO & Pgeie. Thee i
some thought that these two companies owe their success to their appeal to younger
clients.
* Now, suppose we want to ask Ohio college students which company insures their automobiles?
Questions to consider:
Do we have the time or money to ask all Ohioans?
Is a group of 20 Ohioans too small of a sample to answer this question?
Welcome to Chapter 8 Sampling.
8.1 Population vs. Sample
The ____________________________ in a statistical study is the
_________________________ of individuals about which we want information.
A _____________ is a _________ of the population from which we actually collect information.
We can make inferences about a population from a well-drawn sample.
A _____________________________ describes
how to __________________________ from the population.
There are a few excellent examples of sample surveys in use in the United States:
1. The Current Population Survey (CPS) is a joint effort between the Bureau of Labor
Statistics and the U.S. Census Bureau. The CPS samples about 60,000 households each
month from the 50 states and the District of Columbia.
(More details can be found at http://www.census.gov/cps/methodology/ and Example 8.1
on page 200 of the text.)
population
entire
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sample part
sampling design
choose asample
Chapter 8, page 2
2. a. The General Social Survey (GSS) is run by the National Opinion Research Center
(NORC) and funded by the Sociology Program of the National Science Foundation. (See
http://www3.norc.org/GSS+Website/ for more information.)
b. Small fact - Dr. Baker was fortunate to have a summer internship with NORC
(Chicago office) during graduate school. He worked on a Child Immunization study and
assisted with several other projects.
Note: Selected samples should be as representative of the population as much as possible.
We will move on to sampling methods that are
neither are scientific nor representative of the population.
8.2 How to Sample Badly
The design of a statistical study is ________________
if it systematically _____________________________;
it either systematically over- or under-estimates the variable of interest.
In a _________________________________ we collect information
from the members of the population that are ____________________.
Poll: Which company insures your automobile?
(Note: if you do not own a vehicle, then select your preferred company.)
a) State Farm
b) Allstate
c) GEICO
d) Progressive
e) Nationwide
f) Other
biased
favorscertain outcomes
conveniencesample
easiesttoreach
Chapter 8, page 3
A __________________________________ consists of people
who choose themselves to be part of the sample by responding to a broad appeal.
Voluntary response samples are biased
because people with ___________________ are most likely to ____________.
Example: Flo Haysbert contacts CNN; who then presents he Which cany insures your
abile? ei a a 24-hour poll. The responses from college students are separated from
the others and the results are posted. Identify any problems with the data gathered.
This website, retrieved January 28, 2014, affirms the change in top auto insurance companies.
http://www.insurancejournal.com/news/national/2013/12/16/314530.htm
8.3 Simple Random Samples
Convenience samples and voluntary response samples are based upon personal choice and do not
yield representative samples.
Sampling by chance allows all members of the population
an ________________________________ as part of the sample.
A ________________________________ 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
(and every individual has an equal chance of being selected).
Simple random samples can be chosen by assigning random numbers to individuals in the
population of interest.
Technology Tips Computing Descriptive Statistics
TI-83/84 MATH Æ PRB Æ randInt(Lower Bound, Upper Bound, n) Æ Enter.
JMP Cols Æ New Column Æ Name the Column ÆData Type: NumericÆ
Modeling Type: Continuous Æ Initialize Data: Random Æ
Number of rows: Enter your desired sample size Æ Random Integer Æ
Minimum/Maximum: Lower Bound, Upper Bound Æ OK.
voluntaryresponse
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opiniony respond
equalopportunitytobe
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sample SRS
