NCJ Number
63709
Date Published
1979
Length
98 pages
Annotation
IN ANALYZING WHICH ILLINOIS COUNTIES AND CITIES EXPERIENCED A DECLINE IN ROBBERIES AND BURGLARIES, THIS PAPER GIVES DETAILED INSTRUCTIONS ON HOW TO DESCRIBE A TIME SERIES QUICKLY AND EASILY WITH SIMPLE STATISTICS.
Abstract
ROBBERIES AND BURGLARIES FROM 1972 TO 1977 WERE ANALYZED FOR EACH ILLINOIS COUNTY AND LARGE CITY TO SEE IF THE NUMBER OF REPORTED CRIMES HAD DECREASED. FOR 61 PLACES, THERE WAS A SIGNIFICANT DECREASE AND IN 18 OF THESE, A SPECIFIC MONTH APPEARED TO TRIGGER THE DECREASE. THE TIME SERIES SHOWED A TWO SEGMENT LINE INCREASING BEFORE THE CRITICAL MONTH AND DECREASING AFTER IT, GIVING A CLEAR INDICATION OF THE SERIES. THE METHOD OF ANALYSIS USED HAD THREE STAGES OF TESTS. EACH, SUCCEEDING STAGE DESCRIBED THE SERIES IN MORE DETAIL. BECAUSE MANY SERIES ARE ELIMINATED BY THE EARLY SCREEN TEST, THE TIME AND EFFORT REQUIRED TO DO THE MOST DETAILED TEST WAS USED ONLY ON THOSE SERIES WHICH JUSTIFIED IT AND WHERE GREATER DETAIL WAS REQUIRED FOR A PARTICULAR DECISION. EVEN THE MOST DETAILED TEST, HOWEVER, WAS STILL QUICKER TO COMPLETE AND MORE EASILY UNDERSTANDABLE THAN A TIME SERIES ANALYSIS USING MORE SOPHISTICATED TECHNIQUES. THUS THE TESTS ARE A PRACTICAL SOLUTION FOR THE PLANNER OR DECISIONMAKER WHO NEEDS A SIMPLE DESCRIPTION OF A TIME SERIES. THE ADVANTAGE OF THESE SIMPLE TESTS IS THAT THEY ENABLE AN ANALYST TO DESCRIBE A COMPLEX SERIES OF DATA IN NONCOMPLEX TERMS. TABULAR DATA AND A BIBLIOGRAPHY ACCOMPANY THE REPORT. (MJW)