Or

How to make the numbers say whatever you

want.

Free Pizza Lunch with Faculty – Jordan Hall 4th floor lounge

Congrats to the four individuals who were successful in the syllabus challenge

“There are lies, damned lies, and statistics” -- Disraeli

Anecdotal evidence is unreliable

Why does the phone always ring when you’re in the shower?

Determining the difference between chance and real effects

Data = Signal + Noise

Signal = What we’re trying to measure

Noise = Error in our measurement

If noise is random, then as the sample size increases, noise tends to cancel, leaving only signal.

Mean – arithmetic average = x/n

Median – the halfway point

Mode – the most common answer

1

4

3

4

3222

27

Mean = 4.8

Median = 3

Mode = 2

0

6

5

27

4321

27

Mean = 7.5

Median = 4

Mode = 27

1

24

23

26

2211

27

Mean = 10.7

Median = 2

Mode = 1

Range – Overall difference between the highest and lowest scores.

Variance – Average difference from the mean.

1 99 99 911 1111 1111 19

1 11 11 119 1919 1919 19

Identical Range

1 99 99 911 1111 1111 19

6 66 66 713 1414 1414 14

Identical Variance

The Normal Curve

Central Limit Theorem

Any time you have a measure which is created by summing several individual trials of data (Signal + Noise) you will end up with a normal curve

Regression to the mean:

On any given free throw, Bob has an 80% chance of making it.

Bimodal Distributions

Skewed Distributions

Uniform distributions

P value -- The probability that a particular set of data was gained by chance alone.

Statistical Significance – Any P value of less than .05

Correlation measures the strength of a relationship between two variables.

Positive Correlation

0 < R < 1

No Correlation

R = 0

Negative Correlation

-1 < R < 0

Correlation does not imply causation

Correlations can be misleading!!!

A person wearing red is 129 times more likely to be gored by a charging bull!

But what is the base rate?

Mean:

275 minutes

Mean:

53 minutes

98% of Americans have internet access available.

The average temperature in Oklahoma City over the past 100 years is 63.4 degrees. (and each year has been within 1 degree of that average)

Consumer spending on prescription drugs has doubled since 1980.

85% of all car accidents occur within 10 miles of the home.

10 times as many people die each year by plane crashes than train crashes.

During the Spanish-American war, the death rate for soldiers was 9 per 1000. The death rate for civilians in New York City was 16 per 1000.

1 minute 2 minutes

Fluffy O’s Cereal Gives a body Energy!!

10

5??

60

60.5

61

61.5

62

62.5

1st Qtr 2nd Qtr 3rd Qtr 4th Qtr

Earnings

0102030405060708090

100

1st Qtr 2nd Qtr 3rd Qtr 4th Qtr

Earnings

0

5

10

15

20

25

30

35

40

1st Qtr 2nd Qtr 3rd Qtr 4th Qtr

Even when the scale is fine, graphs can still be deceptive

0

5

10

15

20

25

30

35

40

1st Qtr 2nd Qtr 3rd Qtr 4th Qtr

Even when the scale is fine, graphs can still be deceptive

As you can see, Bob earns substantially more than Joe

Joe’s income Bob’s Income

Is it really a two to one ratio that’s being displayed?

Percent of US income going to federal taxes

Percent of US income going to federal taxes

Tylenol is used by 90% doctors for their own aches and pains!

So are Asprin, Ibuprofen, and Bayer!

When Dewey was elected Governor in 1942, the minimum teacher’s salary in some districts was as low as $900 per year. Upon Governor Dewey’s recommendation… the Legislature in 1947 appropriated $32,000,000 out of state surplus to provide an increase in teacher’s salaries. As a result, the minimum salaries of teachers in New York City range from $2500 to $5325.

1) Stanford is the #1 program in psychology

2) I am the only (and therefore #1) student at Stanford studying Decision Errors

Therefore: I am the top student studying Decision Errors in the country.

Group A:I II III IV V6.2 6.4 7.6 6.1 6.2

Group B:I II III IV V6.1 6.3 2.2 6.0 6.2

Is Group A superior to Group B?

The average American sleeps 8 hours a night

The average American sleeps 8.2 hours a night

The average American sleeps 8.2339 hours a night

Main Effects – Effect of one independent variable on the dependent variable

Interactions – When the effectiveness of independent variable X is influenced by another independent variable Y

Curing the Hiccups

Cure 1: Standing on Tiptoes

Cure 2: Holding Breath

Dependent Measure: Number of Hiccups before relief

0

5

10

15

20

25

30

Control Tiptoe

ControlHold Breath

0

5

10

15

20

25

30

Control Tiptoe

ControlHold Breath

0

5

10

15

20

25

30

Control Tiptoe

ControlHold Breath

0

5

10

15

20

25

30

Control Tiptoe

ControlHold Breath

Real effect No effect

Find effect

Don’t find effect

Correct Hit

Correct Miss

False Positive(Type 1)

False Negative(Type II)

Critical Analysis of psychology in the popular press

2-3 pages (double spaced, normal font/margins)

4 articles to choose from

You may discuss the articles with classmates, but under the honor code you must write your own analysis.

1) Statistics are useful for figuring out random noise from real effects

2) Numbers are not absolute, and they can be easily manipulated

3) Always scrutinize data closely, and draw your own conclusions.

4) 85% of all statistics are made up on the spot: the rest are all wrong