Or How to make the numbers say whatever you want.

Free Pizza Lunch with Faculty – Jordan Hall 4 th 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

Mean = 4.8 Median = 3 Mode = 2

Mean = 7.5 Median = 4 Mode = 27

Mean = 10.7 Median = 2 Mode = 1

Range – Overall difference between the highest and lowest scores. Variance – Average difference from the mean.

Identical Range

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 % 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 The death rate for civilians in New York City was 16 per 1000.

1 minute2 minutes Fluffy O’s Cereal Gives a body Energy!! 10 5 ??

Earnings

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

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: IIIIIIIVV Group B: IIIIIIIVV 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 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

Real effectNo 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