Wednesday April 9, 2014

 

Copycat Bank Robbers

Police departments aren't very happy when a successful bank heist is reported in the media. 

They obviously fear that so-called copycat bank robbers will be inspired and emboldened by the success of the reported robbery.  To determine if a copycat effect exists, a study by the Australian Centre for Policing Research looked at the number of bank robberies in the 7 days before and
the 7 days after a successful bank robbery that was covered in the media.  If the mean number of bank robberies is higher in the 7 days after the successful bank robbery, then this may be evidence of a copycat effect.  Bring up the data set copycat_robberies.mtw, which
presents data that is consistent with summary quantities given in the report.  The data are comprised of the number of robberies before and after 49 successful bank robberies covered by the media.
Test the data for the presence of a copycat effect using significance level alpha=0.05 --- state hypotheses, report test statistic and p-value, and give your conclusions.

 


Memory Recall Study     

In a study of memory recall, 8 students from a large psychology class were selected at random and
given 10 minutes to memorize a list of 20 unrelated words.  Each student was asked to list as many

words as he or she could remember both 1 hour and 24 hours after.  The data are found in the Minitab worksheet memory_recall_1_24.mtw.

(a)  Is there evidence of a "forgetfulness effect"?  In other words, is there a significant loss of the
number of memorized words, on average, from 1 to 24 hours?  Use significance level alpha=0.01.

(b)  Is there evidence that the number of words recalled after 1 hour exceeds the number recalled
after 24 hours by more than 3 words, on average? Again, use alpha=0.01.

(c) Find a 99% confidence interval for the mean number of words "forgotten" between 1 and 24
hours after reading the word list.