Gary Klass Department of Politics and Government Illinois State University

J UST P LAIN D ATA A NALYSIS Part I Statistical Fallacies Gary Klass Department of Politics and Government Illinois State University

F ROM LAST YEARS ’ CONFERENCE : Moving Practitioners Beyond Descriptive Statistics Saturday, October 18, :30 a.m. - 12:30 p.m. Seminar Description: Statistical analysis is very important with regard to reports, projects, policy, and the general understanding of information processed on a daily basis. Many people are intimidated by mathematics and statistics, which causes an overreliance on simple descriptive statistics such as means, standard deviations, rates, and percent changes. These simple descriptive statistics all have limitations, however. The primary goal of this presentation is to identify the limitations of descriptive statistics and explore more meaningful bivariate and multivariate analyses, such as z-scores, t- tests, ANOVA, and regression. Instructor: Jamie Price, President Socialphenom, Inc. West Palm Beach, Florida

S TATISTICAL F ALLACIES An argument: – Premises (evidence and reasoning) in support of a conclusion An argument fallacy: – When the premises, even if true, do not support a conclusion (Examples: false cause, slippery slope, ad hominem, straw man, red herring…). A statistical fallacy: – When the data do not support the conclusion.

C HERRY P ICKING : H OW P RESIDENT B USH L OWERED THE P OVERTY R ATE (Bill O’Reilly)

C HERRY P ICKING : D ISTRIBUTION OF 248 Z - SCORES IN 17 POLITICAL ECONOMY STUDIES (Tufte, Beautiful Evidence)

C HERRY P ICKING : C UMULATIVE % CHANGE IN INCOME TAX REVENUES * AFTER R EAGAN AND C LINTON TAX CHANGES * Constant dollars

C HERRY P ICKING : C UMULATIVE % CHANGE IN INCOME TAX REVENUES * AFTER R EAGAN AND C LINTON TAX CHANGES * Constant dollars

M EASUREMENT R ELIABILITY : T WO M EASURES OF V IOLENT C RIME (per 1,000 population)

R EGRESSION A RTIFACT : S ENATE O IL P RICE S PECULATION B ILL AND C RUDE O IL P RICES *

R ESERVE C AUSATION : P ROSECUTION R ATE OF P UBLIC O FFICIALS AND V OTER T URNOUT,

R ESERVE C AUSATION : F ELONY A RREST R ATIO AND V IOLENT C RIME R ATE, 2008: N EW Y ORK C OUNTIES (excl. NYC)

P OPULATION M ORTALITY : E NROLLMENT AND F IRST I NTERNATIONAL S CIENCE S TUDY R ESULTS, F INAL Y EAR OF S ECONDARY S CHOOL

T HE T REND IS NOT YOUR F RIEND : A VERAGE C ONTRACT P RICE OF N EW O NE -F AMILY H OUSES (2000 dollars)

R ATE OF C HANGE F ALLACY :

R ATE OF C HANGE F ALLACY : " M INORITIES IN THE U.S. INCREASED THEIR LEVELS OF HOMEOWNERSHIP AT A FASTER CLIP THAN WHITES DURING THE RECENT HOUSING BOOM." -WSJ 5/13/09WSJ 5/13/ Change Homeownership Rates Black % Hispanic % Asian % White % Home Non-Ownership Rates Black % Hispanic % Asian % White %

Graphical Distortion: Average Tuition and Fees: 4-year Public and Private Universities

D OMINANT D ENOMINATOR “Bill Clinton and a GOP Congress balanced the budget by withdrawing a ‘peace dividend’ at a time when al Qaeda was declaring war” (2004). --WSJ 8/9/04

Dominant Denominator: Clinton defense budgets: % of GDP and in constant dollars

“Crime halved under Mr. Giuliani and murders fell by two-thirds, transforming New York from one of the most dangerous cities in America to one of the safest.” “From America's mayor to America's President?,” The Economist.com (3 May, 2007)

R OBBERY R ATES, T EN L ARGEST C ITIES, *BJS: Data Online

N EW Y ORK C ITY C RIMES, (Thousands)

C OUNTER A RGUMENTS Crime went down in other cities too (Freakonomics) The national economy improved Regression artifact – end of crack epidemic William Bratton, not Giuliani, deserves credit Decline started under Dinkins Most of the reduction was for minor crimes Bad data: CompStat encouraged underreporting of crime

V IOLENT C RIME R ATES, N EW Y ORK C ITY, (per 100,000 population)

FBI\UCR V IOLENT C RIME R ATES : 69 L ARGEST C ITIES, 2007 (population > 250,000)

V IOLENT AND P ROPERTY I NDEX C RIMES, N EW Y ORK C ITY, (thousands) -46%

FBI AND NCVS V IOLENT C RIME R ATES : 69 L ARGEST C ITIES, 2007 (population > 250,000)

M URDER R ATES : N EW Y ORK C ITY AND 69 L ARGEST C ITIES, 2007 ( POPULATION > 250,000)

M URDER R ATES : N EW Y ORK AND 69 L ARGEST C ITIES, 2007 (population > 250,000)

T HE E CONOMY ?

D INKINS AND POLICE HIRING ? S WORN O FFICERS, N EW Y ORK C ITY P OLICE D EPARTMENT, AND V IOLENT C RIME R ATE General Accounting Office. “COMMUNITY POLICING GRANTS COPS Grants Were a Modest Contributor to Declines in Crime in the 1990s”

C HANGE IN C RIME R ATES AND S WORN P OLICE P ERSONNEL, IN THE 1990 S, 58 L ARGEST C ITIES