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How to Lie with Statistics is a wonderful book on how statistics and numbers, while they give the impression of “objectivity”, can easily be misread, misinterpreted or flat out “massaged” to sway people’s opinions.

Bullet Summary

• Watch out for missing data: 3 days to cure a cold with X drug is no good if you healed quicker without
• Always ask yourself what biases could go into a survey/statistics/sample
• Ask yourself if the individual presenting the statistics might have second motives

Full Summary

The ideal sample is large, measures only one trait while controlling the other, and removes all sorts of biases.
Such a sample is hard to obtain, and most “statistics” instead have all sorts of biases.

How to Lie with Statistics lists a few of them.

Statistics Biases

The following biases are some of the most common and and highly disruptive biases when measuring a sample:

#1. Asking People

People tend to answer with what makes them look good. Or with what they wish they’d do, or with what they would like to do.

Not always they will answer instead with what they actually do.

Even when you meet a fella who wants to tell you the truth and nothing but the truth, will he be able to remember exactly what you’re asking for?

Thus if you ask people what they actually like, they will rarely come up with the truth.

#2. Self-Selection Bias

Many studies are flawed by design.
For example if I send a questionnaire out most people replying will be people who maybe have more time to reply.

If I ring people’s doors to ask question it will be people who are more often at home -unemployed, non-travelers?-.

Even if I stop people in the street I will end up selecting friendlier or more agreeable personalities.

#3. Pleasing the Interviewer

Whenever I ask a question about touchy subjects there might be an in-built bias in willing to please the interviewer.
If I ask for example what do they think of, say, racism, few people will be open and frank about it.

#4. Small Sample Biases

It’s easy to come up with a true statistics that though means very little or that is actually deceitfully misleading.

For example if you wanted to prove that a medication is very effective in curing a cold, you could assemble many small sample. Then you can measure how long it takes to get better in each.

Since the samples are small, normal variation will likely give you a group that, by chance, healed quicker.
And you can publish the result of the group that fared the better

#5. Intervening Factors Biases

Another issue of comparing statistics across countries or times and, in general, in real life, is that of intervening factors that it’s difficult to account for.

For example one study once link milk to cancer because countries that consumed more milk had higher incidence of cancer than countries with a low milk consumption.

Darrell Huff explains that the countries with more milk consumption were also richer and lived longer. That by itself can explain the higher incidence of cancer. And if you also factor in that cancer is more likely to happen in old age, that could explain all by itself the difference in cancer rates.
No milk withstanding.

Changing of Meaning

Sometimes bureaus change their description or what a word means, or a word comes to acquire a totally different meaning.

So for example when you calculate the number of “farms”, you should adjust for the changes in census, because what is considered today a “farm” is not the same as it was fifty years ago.

Bigger Charts

There are many ways to “massage” your charts:

• Raise the starting point

To show bigger improvements you can make a chart start not at zero, but at the latest number in your data set.

For example, if you want to show an improvement from 20 to 22 and then 23.5 and you start your chart from zero, the improvement will look small.
But if you make the chart start at 20, it will look like a huge change.

• Leverage Volume

If you want to show the increase of something -say, salaries- a fair way would be to use bar charts that only change in height.

If you want to make the increase look bigger though you can use geometrical shapes. Say for example you choose the icon “bag of money” to show the salaries increase.
When you increase the height of the bag of money you don’t just change the height, but you also change the width. The result is that your bag of money will acquire a total area that is 4 times bigger, not twice.

• Don’t Label the Axis

Another trick is to not put measures and labels on a chart.
Make the reader do his own assumption and if the chart looks impressive he will make favorable assumptions.

Proving Without Proving

This one is almost pure marketing.

Say that you cannot prove that your new drug helps cure a cold. But you can prove that it kills thousands of germs. Maybe even more than your previous drugs. Maybe 30% more?
It might not to a thing to help people overcome a cold, but it certainly sounds good.

Or an advertisers could say that physicians smoke brand X of cigarettes more than any other cigarettes. But does that mean anything? Physicians might not have much insider knowledge on “healthier cigarettes”. As a matter of fact, there is no such thing as healthy tobacco.

Percentage Increases/Decreases

When people talk about an increase of 10%, you should always wonder: increase compared to what? The previous month, the previous week? And was it an increase across the board or did they pick a figure that increased the most?

Also people who want to give different impressions can easily switch from percentages to whole number depending on which one sounds better.

The percentage drop is even easier to massage.
For example describing the move from 13% to 10% as “a drop of 3 percentage points” sounds much better than “a decrease of 23%”.

Cherry-Picking the Best Figure

Similarly, you can express the same fact by calling it in many different ways, depending on what your goals are and what sounds more impressive -or less scary-.
For example:

• 2% percent return on sales
• 12% return on investment
• 5 million profit
• 35% increase in profits

Correlation Not Causation

And here is the big one, one that I have been criticizing in so many of my book reviews.

Many publications use correlation to imply causation.
Take for example the famous case of “studying leads to higher salary”. While that makes a lot of sense, it’s not so straightforward.

Kids who to go to college are disproportionately bright and rich.
The bright and rich would have likely earned more than non-college degree individuals even without a college degree.
And it’s not true that “the more you study, the more you earn”.

The most dishonest individuals can also look for a correlation and then plug a cause that works well for them.
Politicians do it often. For example Donald Trump took the crime statistics of a single US city where crime had increased. And blamed democrats on it.

Also read:

• Fooled by Randomness

Real Life Applications

Always Critically Read Data
Don’t be ready to believe the numbers “because they’re numbers”. Anything can be bent to fit a propaganda or a biased individual.

CONS

Don’t Stop at First Critical Level!
One danger I see with How to Lie with Statistics is that people might stop at the first level: taking apart a statistics without reflecting that actually even a flawed statistics might be a strong warning signal or it may capture an important trend.
For example the author criticizes the statistics that women who attend college marry less that the national average while men marry more. Instead of dismissing that result, one should ask if that makes sense and why it’s happening.
My guess is that it makes sense because more women are attending college -read a scientific approach a to dating-.

PROS

Great Education Against Cheats and Power Movers
The more people read books like this, the fewer the people that are easy to dupe and swindle.
And that will make for better world to live in.

Short and To The Point
No fluff, no repetition: I love it.

Review

How to Lie with Statistics is a five stars, must read book for those who aren’t aware of the pitfalls and “sneaky tricks” that hide behind statistics -ie.: most of us-.

I believe that How to Lie with Statistics can make for a better world.
The more people read it, the more we will we can think critically, assess claims better, buy better and even vote better.

It’s also good for a psychological understanding in a way. With How to Lie with Statistics you will learn how our mind can unwittingly make wrong connections.
And, of course, it’s great for power moves. Because you will learn how unscrupulous researchers, companies and journalists can willfully manipulate data to sway people.

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