CHS Statistics
1.3: Uses and Abuses of Statistics
Objective: To identify common errors and misuses of
statistics
Practical Uses of Statistics
 Poll results are used to determine the television shows
we watch and the products we purchase.
 Manufacturers provide better products at lower costs by
using statistical control tools, such as control charts.
 Diseases are controlled through analyses designed to
anticipate epidemics.
 Endangered species of fish and other wildlife are
protected through regulations and laws that react to
statistical estimates of changing population sizes.
 Through statistical analysis of fatality rates, legislators
can better justify laws, such as those governing air
pollution, auto inspections, seat belt and air bag use,
and drunk driving.
These are just a few examples of the many practical uses of
statistics!
Abuses of Statistics
 Some people will use statistics in which the data
are presented in ways that are designed to be
misleading.
 Some abuses are not intentional, but some are!
 “Statistics show far fewer skateboarding
injuries in the winter, while sledding
injuries are more common.”
 Does this seem like a valid statement?
What could be a reason for such misleading
statistics?
Abuses of Statistics (continued)
 Common ways in which data are misleading:
1) Bad samples
A major source of deceptive statistics is the
use of inappropriate methods to collect data.
Self-selected survey – (voluntary
response sample) is one in which the
respondents themselves decide whether to
be included
In such surveys, people with strong
opinions are more likely to participate, so
the obtained responses are not
necessarily representative of the whole
population.
Abuses of Statistics (continued)
 Common ways in which data are misleading:
2) Small Samples
 It can be very misleading to make broad
conclusions or inferences based on samples
that are far too small.
 Example: Children’s Defense Fund’s
publication of Children Out of School in
America reported that among secondary
school students suspended in one region,
67% were suspended at least three times.
That statistic was based off of only three
students, and the media reports failed to
mention that!
Abuses of Statistics (continued)
 Common ways in which data are misleading:
3) Loaded Questions
 Survey questions can be worded to elicit a desired response.
 A “loaded” item uses emotionally charged words – words
that have a strong negative or positive.
 Example: The University of Pittsburgh should stop
wasting student activities funds on elitist organizations
such as fraternities and sororities.
A. strongly agree
B. agree
C. neutral
D. disagree
E. strongly disagree
This is a loaded item because of the use of the
phrases “wasting funds” and “elitist organizations.” It
would be improved by making the wording more
neutral.
Abuses of Statistics (continued)
 Common ways in which data are misleading:
4) Misleading Graphs
 Many visual graphs (especially bar charts and pie charts)
exaggerate or hide the true meaning of the data. Using
different increments or not following the Area Principle is a
key way to exaggerate, so be careful when reading charts!
Abuses of Statistics (continued)
 Common ways in which data are misleading:
4) Misleading Graphs – More examples
Abuses of Statistics (continued)
 Common ways in which data are misleading:
5) Pictographs
 Using pictures and three-dimensional objects as bars in histograms and bar
charts can be misleading and, again, not follow the Area Principle.
Abuses of Statistics (continued)
 Common ways in which data are misleading:
6) Precise Numbers
Being precise is not always accurate. Saying there are
203,144,036 vehicles in the Southeast region. Since
this number is an estimate, it would be better to say
about 203 million.
Abuses of Statistics (continued)
 Common ways in which data are misleading:
7) Distorted Percentages
Be careful with interpretation of
percentages:
 An ad from Continental Airlines referring to
lost baggage; “… an area where we’ve
already improved 100% in the last six
months.”
 The New York Times took this to mean
there is no lost baggage, which has
never been achieved by Continental
Airlines.
Abuses of Statistics (continued)
 Common ways in which data are misleading:
8) Partial Pictures
“Ninety percent of all our cars sold in this
country in the last 10 years are still on the
road.”
 Consumers were impressed; however, the
dealer failed to mention that 90% of the cars
that the dealer sold were in the last 3 years.
Abuses of Statistics (continued)
 Common ways in which data are misleading:
9) Deliberate Distortions
Be careful to accurately interpret survey
results. Hertz sued Avis because Avis said
they were the winner of the survey among
car rental companies. When Hertz
requested the actual survey results, the
responses disappeared and the magazine
coordinator who published the survey result
statement resigned.
Homework
Pp. 15 – 16 # 1 – 6, 8 – 12, 14