An auditor collected a random sample of about 100 invoices sent out in the current fiscal year and compared the amounts of these invoices to those of a second random sample of invoices in the prior fiscal year. These box plots summarize the amounts (in dollars) of the two sets of invoices.

Would you suggest that the auditor perform a two- sample t-test to compare the mean values of these invoices, or can you suggest one (or more) lurking factors that should be taken into account prior to the comparison?

Transcribed Image Text:

60,000 50,000 40,000o 30,000 20,000 10,000 0 2007 Year 2008 Year Number Mean Std Dev 2007 200810 20,582.7 8,763.01 21,713.4 8,245.42