•
In reality, by the time the Globe released the poll, it
contained old information from January 2
–
6, 2010. Even
more problematic was that the poll included people who
said that they were unlikely to vote!
16
Example 3•Starbucks Corp., the world’s largest coffee-shop operator, reported that sales at stores open at least a year climbed 4% at home and abroad in the quarter ended December 27, 2009. Chief Financial Officer Troy Alstead said that “the U.S. is back in a good track and the international business has similarly picked up. … Traffic is really coming back. It’s a good sign for what we’re going to see for the rest of the year” (, January 20, 2010).
17
Problem with conclusion
•
In order to calculate same-store sales growth, which
compares how much each store in the chain is selling
compared with a year ago, we remove stores that have
closed.
•
Given that Starbucks closed more than 800 stores over
the past few years to counter large sales declines, it is
likely that the sales increases in many of the stores were
caused by traffic from nearby, recently closed stores. In
this case, same-store sales growth may overstate the
overall health of Starbucks.
18
Example 4
•
Researchers at the University of Pennsylvania Medical
Center found that infants who sleep with a nightlight are
much more likely to develop myopia later in life (Nature,
May 1999).
19
Problem with conclusion
•
This example appears to commit the correlation-to-
causation fallacy. Even if two variables are highly
correlated, one does not necessarily cause the other.
•
Spurious correlation can make two variables appear
closely related when no causal relation exists.
•
In a follow-up study, researchers at The Ohio State
University found no link between infants who sleep with
a nightlight and the development of myopia (Nature,
March 2000).
20
Statistics
•
….. is the methodology of extracting useful information
from a data set.
21
Statistics
•
….. is a way of reasoning, along with a collection of
tools and methods, designed to help us understand the
world.
22
Statistics
Statistics
Descriptive
Statistics
Inferential
Statistics
23
Descriptive Statistics
•
Refers to the summary of important aspects of a data
set.
•
This includes collecting data, organizing the data, and
then presenting the data in the form of charts and
tables.
