RECOGNIZING STATISTICAL SLIPS

Presented by:

Hellaisna N. G

200912570094

Statistics is....• Plural

Statistics is information about any phenomenon or activity expressed in numerical form, such as vital statistics, college enrollment figures, and opinion poll percentages.

• Singular

Statistics is the art & science of collecting, presenting, analyzing, and interpreting numerical data.

Common Statistical Slips• The Deceptive Sample• The Misleading Average• Plausible Charts and Graphs• Presenting the Facts without a Reference

Point

The Deceptive Sample

Error in sampling.

Interpretation of statistic output doesn’t represent true fact of total of population.

How could this happen: Sample bias or too small Sample chosen to prove the writer’s point

Brand Manager of Head & Shoulders released the statement:

“Head & Shoulders is the best brand for shampoo category in Indonesia.”

*based on national consumer survey in 2010.

The Questions are:

Are samples chosen by pure random method?How many samples are surveyed?Is it enough to represent total of Indonesian population?

The Misleading Average

• Generating a wrong conclusion because the data didn’t distribute normal.

• Example:

“Indonesia can’t acces a soft loan from the World Bank because its per capita income is

above average.”

So, what’s the big deal??

It is because the World Bank put their

conclusion on per capita income.

But, what about the data?Does it show a true fact about Indonesia?

Income (I) Population (P) Sum of P x I

US$ 100 50 US$ 5.000

US$ 200 150 US$ 30.000

US$ 300 300 US$ 90.000

US$ 400 250 US$ 100.000

US$ 500 200 US$ 100.000

US$ 600 0 US$ 0

US$ 700 0 US$ 0

US$ 800 0 US$ 0

US$ 900 2000 US$ 18.000

US$ 1000 150 US$ 150.000

TOTAL 1.300 US$ 655.000

Indonesia’s Per Capita Income is US$ 503,85.-

That is why Indonesia can’t access any soft loan from the World Bank.note: only country with Per Capita less than US$ 500 can get a soft loan from the World Bank

In fact, Indonesian income is dominated by the middle-lower income

Plausible Charts and Graphs

• Manipulating charts or graphs to convey almost any desired impression.

What do feel when watching this chart?

Same like before Graph 2 is more impressive

Presenting the Facts Without a Reference Point

• Present a statistical result without suficient data in presentation.

The graph tells us students behavior on everage is good.The question:What is definition of those scale (0-10)

Exercise 1

“Students in Class Xo are good in mathematics. Data shows the average of their mathematics’ score is above 7.”• The Deceptive Sample• The Misleading Average• Plausible Charts and Graphs• Presenting the Facts Without a Reference point

Please try again

Sorry!! Wrong answer..

Hmmm... I don’t think that’s the

answer

Let’s check the exercise one more time!

back

That’s not the answer

The Answer is….

The Misleading

Average

Exercise 2

“The level of public health is going worse.”

• The Deceptive Sample• The Misleading Average• Plausible Charts and Graphs• Presenting the Facts

Without a Reference point

Please try again

Sorry!! Wrong answer..

Hmmm... I don’t think that’s the

answer

Let’s check the exercise one more time!

back

That’s not the answer

Presenting the Facts Without a Preference

Point

What is the answer?

Exercise 3

“94% of Indonesian women agree that the Garnier light cream can make their skin more shinning, 92% agree the Garnier white cream can reduce oil in their face, 93% agree it can reduce black spot of acne.”

• The Deceptive Sample• The Misleading Average• Plausible Charts and Graphs• Presenting the Facts Without a Reference point

Please try again

Sorry!! Wrong answer..

Hmmm... I don’t think that’s the

answer

Let’s check the exercise one more time!

back

That’s not the answer

Answer is…

The Deceptive

Sample

Conclusion

• The good statistics are:1. Sampling uses a random sampling method with

sufficient data to represent the total group.

2. There is no individual interests behind the survey.

3. No outlier in the data.

4. Don’t judge the fact by the graphs or charts.

5. Statistical output must attach a referenced point as a comparison standard.