KEY to
BUS271 Inclass Quiz over Chapter 1
20110825
[Over 54 points]
102. [Chapter 1; 6 points] (Definitions)
Explain the difference between a “population” and a “sample”. Does this
distinction reside in the data, or does it depend on how we plan to use the
data?
To answer the second question first: the distinction is not found in the
data, but in the use to which we want to put the data. (If I hand you a
data set for 200 people and ask whether you can tell if this is a sample or
a population, you
can’t …)
If the group of entities we want to ask questions about is limited to the
entities which contributed data to the data set, then the data set is a
population
data set (a census). Example: I want to know the average
height for members of this class
, so I measure everybody’s height.
If we want to ask questions about a group that’s bigger than the group
which contributed data, then the data set is a sample
data set. Example: I
want to use class data to estimate the average height for all SUSCC
students.
(Note: For our data sample to be a valid sample, the group which
contributed the data must be part of (a subset of) the intended
population!)
103. [Chapter 1; 3 points] (Definitions)
Define what we mean by an “outlier.” Why do we care about outlier
s?
An “outlier” is a data value that is very small or very large: it is “far
from” the mean by some measure or other. (We have discussed 2
different ways of identifying outliers.)
We worry about outliers because they
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 Spring '09
 Business, Statistics, Household income in the United States

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