"Lies, damned lies, statistics ! ” How this may influence your decision making in Investing ?
How to Lie with statistics!
As an investor, we have been bombarded by news and statistics
every minutes and second, as we know well, some of this news been exaggerated
and statistics or figures used also questionable.
We need to understand
the figure behind these statistics and how is it derived to ensure that we have
not been lied by statistics.
Darrell Huff gives people the tools to talk back to statistics.
"There is terror in
numbers and nowhere does this terror translate to blind acceptance of authority
more than in the slippery world of averages, correlations, graphs, and trends.
“ writes Darrell Huff.
What was true in
1954 is just as true today. According to Huff, below are just a few common
tactics used to influence readers by using some “twisted or distorted “ ways
of presenting their data in the presentation.
“The Gee-Whiz Graph" and “ The One Dimension Picture “
This is about how the graphical display of statistics can be
twisted so that one can get any desired result, though the statistics figure aren't
changed. Such graphic or picture
will give us “ eye illusion “ in order for the presenter to achieve their
desire message or result.
For example, the below charts show the effect
of “impact “ by changing the scale and starting point of the Y-axis, by doing
this, the presenter would be able to “shock the reader “ and win the
argument.
Correlation doesn’t mean causation :
Duff also points out the fallacy of correlation. Sometimes
the two variables have a very strong correlation and both the statistical and
mathematical requirements are met but that doesn’t mean it has causation.
For example, there is a strong correlation between a school
child's height and the child's score on a given spelling test - taller kids do
better. The fact is a lot less surprising when you see that first graders tend
to be smaller than sixth graders, and tend to know fewer words. Maybe the
example sounds silly but no sillier than lots of the numbers in the news every
day.
'Skirt Length Theory'
in Wall-street.
 |
| <Image credit to: socionomics.net> |
The idea that skirt lengths are a predictor of the stock market direction. According to the theory, if
skirts are short, it means the markets are going up.
And if the skirt is long, it
means the markets are heading down. Also called the Hemline Theory.
What do you think?
Below weblink shown some of the very fascinating charts in
plotting two different variables in very high correlation but no causation at all.
Few charts to shown from the above link: just for fun!
<image credit : fastcodesign.com>
Poorly chosen and the problem of average :
“Statistician,
a person who lays with his head in an oven and his feet in a deep freeze
stating, On the average, I feel comfortable”- Bruce Grossman.
Below are the annual returns
for the S&P 500. The red circles represent the years that were within half
a per cent of the average return. If the average return has occurred in just
three out of ninety years, you should probably be very sceptical of anyone
crafting a narrative based solely on historical averages.
Same apply to STI Index
investing, when one buying into Index ETF base on long term average return of
7-8%, but bear in mind that it was based on a long period of average, at
anyone time, the return could be from +/- 20 to 40%. Investors may feel “shock” that even with ETF Index investing, the volatility could
be huge on a yearly basis.
This is another one of my favourite charts on “statistically
bias on average “.
The sample with Build-in bias.
Quoted from Wikipedia: “In statistics, sampling
bias is a bias in which a sample is collected in such a way that some
members of the intended population are less likely to be included than others.
It results in a biased sample, a non-random sample of a population (or non-human factors)
in which all individuals, or instances, were not equally likely to have been
selected. If this is not
accounted for, results can be erroneously attributed to the phenomenon under
study rather than to the method of sampling.”
The most common type of sampling
bias is “ Selection from a specific real area.” For example, a survey of high school students
to measure teenage use of illegal drugs will be a biased sample because it does
not include home-schooled students or dropouts.
A sample is also biased if
certain members are underrepresented or overrepresented relative to others in
the population.
For example, a "man on the street" interview which
selects people who walk by a certain location is going to have an
overrepresentation of healthy individuals who are more likely to be out of the
home than individuals with a chronic illness. This may be an extreme form of
biased sampling, because certain members of the population are totally excluded
from the sample.
Ways to Avoid Being Fooled By Statistics
This LINK may give you some clues :
I would like to end my post by below link of Video from TED-Talk: by Sebastian Wernicke on Lies, damned lies, statistics.
Cheers!
Quote Of The Day :
Good sharing the dangers of all that statistical noise around us. In our society, we teach most children reading and writing, but not statistical thinking. Could it be that we all suffer from "innumeracy"?
ReplyDeleteThe most important thing to remember about using statistics effectively. Statistics are rarely meaningful in and of themselves. Statistics will, and should, almost always be used to illustrate a relationship. It’s more important to remember the relationship than the number.
It is a prudent approach to take any statistic you read with a grain of salt. Chances are it is made up, will be revised or is just plain misapplied. And that includes GDP and unemployment statistics as well. Still so many people draw investment decisions from minuscule movements in those KPIs.
Hi Andy,
DeleteThanks for the comments and well said! Yes, we must always take what we read & figure with a grain of salt. ..yap. .I do have big ? on GDP figure. .as we know well. .much activities not been counted for. .eg underground activities, contributions from mothers on household activities. .etc..
I like this joke on GDP the most : one day , two economist were arguing on certain theory they are working with ...while walking back to their dormitory. .one of the economist (A) saw a dog poop on the ground and challenge the other to eat it and he will pay him a million dollar, else he have to accept the theory he has proposed. . It order to prove that his (B) is much more accurate. .he decided to take and eat it ...Next , after a while , they saw another dog's poop on the grass. .now economist (B) challenge (A) with the same tactics. .economist A also decided to take the challenge and eat it so as to prove that his theory is more accurate. .."
At the end of the day. ..both economist has just created and contributed $2 millions to the GDP..
Hahaha. .☺☺cheers