use & misuse of statistics as 12.4.6 12.4.1
TRANSCRIPT
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
1/13
Use & MisuseUse & Misuseofof
StatisticsStatistics
A S 12.4.6; 12.4.1
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
2/13
Statistics & graphs send avery powerful message topeople.
Graphs have the capability tostrengthen suggestions about
the data based on the type ofgraph, the colours used andother tools.
Just because you see a graphdoes not mean you shouldbelieve it.Examine carefully where thedata came from and what it is
telling you.
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
3/13
Sources of BiasSources of BiasBias is any influence that unreasonablyaffects or sways the results of a samplesurvey or census.
This includes bad & small samples,
loaded questions, non-response bias,interviewer bias, order of questions,processing errors etc.
A survey on the effects of
passive smoking,sponsored by a majortobacco manufacturer, ishardly likely to be
impartial.
e.g
.
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
4/13
Youth unemployment is over 30%;therefore 30%of S.A.s 15-19 year olds are unemployed.
Misunderstanding of definition of
unemployment as most are stillstudents.
Give possible problems with thestatistics or survey questions in thefollowing?
Too little money is being spent on welfare.
Loaded question
Would you say that traffic contributesmore orless to air pollution than industry?
Order of question putting traffic first
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
5/13
Misleading GraphsMisleading GraphsGraphs can be misleading in a number ofways - scale, labels, size or missing dataetc.
There is no scale on the vertical axis. Thisperspective makes it look as though thesales for 1995 were far more than those forany other year. In fact they were identical tothose for 1997.
This 3D bar chart
looks attractive,but it is verymisleading.Why?
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
6/13
What is this graphbelow trying to tell
us?
Why is the graph a poorgraph?
Puffed oats hasalmost no sugarcompared to othercereals.
No scale on axisAlthough less, it
still has a lot of
What do you now notice?
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
7/13
http://mathrocks.thebernas.net/IntMath3/
Why isthis graphmisleadin
g?
It looks as if smoking is the main cause ofdeath.Also other causes are missing cancer,heart attacks, strokes, people who did not
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
8/13
So to correctly interpret a graph, we
should analyze the numericalinformation given in the graphinstead of being mislead by its
general shape.
The purpose of using
graphs is usually tocompare trends or generalmagnitudes rather thanprovide precise data
points. Use a table to showprecise data points.
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
9/13
Misleading numbersMisleading numbers
The proper choice of an average
statistic isnot always the mean. Medians are often
moreinformative. The problem with means is
thatthey can be easily skewed by extreme
high orlow values (outliers).
Be aware of the scale used to measurethe data.A ranking of 1 to 3 is used, where 1 =
best, to rank your drink preference.So if you prefer Coke only marginallymore than Pepsi, a ranking of 1 forCoke and 2 for Pepsi implies that you
like Coke twice as much as Pepsi.
e.g
.
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
10/13
bonus for a full-time employee of theCompany
is R31,417. Use the data in the table
below todetermine if this is an accurate
statement.Annual Income (R)
25,000 18,000 32,00028,000
22,000 19,000 34,00092,00029,000 31,000 21,00026,000
The news article used the mean of thebonuses for the average annual bonus.
All but 3 of the bonuses are below thisvalue. The bonus of R92,000 has distortedthe value of the mean. A better measurefor the annual bonus would be the median,
R27,000.
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
11/13
We'rewinning
cancer fightThe Weekend Australian, Saturday May 9, 1998Is there anythingmisleading aboutthe graphs?Explain.
The graphs use differentscales. It is difficult tocompare cancer
incidence rates for menand women. Also itseems as if theres agreater decrease in the
rate for the men from
Media exampleMedia example
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
12/13
Source: The Mercury, 10 November, 1997
Di: 98% say it was a plotBritish Sunday newspaper The People revealedyesterday that nearly everyone who responded to
a survey organised by the paper believe Diana,Princess of Wales, was murdered. It says morethan 98 per cent of 5,600 people who rang ahotline answered "yes" to the question: "Were
Diana and Dodi killed as part of a secretoperation?" Only 93 said they believed the crashwas an accident.
It is a voluntary phone-in poll. Usuallybiased as only those with a strong viewphone in. Also the way in which thequestion was asked encouraged a "yes"response?
Why would you question the results of this
survey?
-
8/4/2019 Use & Misuse of Statistics as 12.4.6 12.4.1
13/13
Find three newspaper or magazine
articles that contain incorrect ormisleading analysis or presentation
of the statistics.
For each article, hand in a copy ofthe article and a short critique of theincorrect or misleading analysis or
presentation of the statistics in thearticle.
Ta
sk