FBI Bank Crime Statistics Bank Robberies in the U.S. Per Weekday from January 2009 through June 2011
Goals <ul><ul><li>The Federal Bureau of Investigation tracks bank robberies across the U.S. </li></ul></ul><ul><ul><li>One statistic they maintain is on what day of the week these robberies occur. </li></ul></ul><ul><ul><li>We investigate bank robberies that occur during the normal work week (i.e. Monday through Friday). </li></ul></ul><ul><ul><li>The data analyzed occurred in the last ten quarters beginning January 2009 and ending June 2011. </li></ul></ul>
Summary of Values Minimum = 165 Q1 = 205.00 Q2 = 220.50 Q3 = 242.00 Maximum = 343 Mean = 223.88 Median = 220.50 Mode = 208.00 Std. Dev. = 32.00 Interquartile Range (IQR) = 37.00 Lower Fence = 149.50 Upper Fence = 297.50
Empirical Rule There is only a 0.5% chance that more than 316 robberies would occur on any given weekday but 343 robberies occurred on a Friday in the first quarter of 2009!
Box and Whisker Plot Fridays in the first quarter of 2009 were the only outlier observed in the data analyzed.
Setting the Record What are the chances we will see another weekday with 343 or more robberies?
Hypothesis Test The FBI are developing their 2012 Fiscal Year budget and need to know how many special agents to train in bank robbery investigation. The mean number of robberies per weekday decreased to 191.3 over the last two quarters. Can the FBI safely assume that the number of robberies is decreasing with a significance of 0.02?
Confidence The Director of the FBI has requested that the agency be able to handle the average case load the vast majority of the time. Between which means can the agency expect the number of robberies to fluctuate 98% of the time?