In order to control costs, a company wishes to study the amount
of money its sales force spends entertaining clients. The following
is a random sample of six entertainment expenses (dinner costs for
four people) from expense reports submitted by members of the sales
force.
$
309
$
319
$
343
$
364
$
341
$
331
(a) Calculate x⎯⎯x¯ , s2,
and s for the expense data. (Round
"Mean" and "Variances" to 2 decimal places and "Standard Deviation"
to 3 decimal places.)
(b) Assuming that the distribution of
entertainment expenses is approximately normally distributed,
calculate estimates of tolerance intervals containing 68.26
percent, 95.44 percent, and 99.73 percent of all entertainment
expenses by the sales force. (Round intermediate
calculations and final answers to 2 decimals.)
(c) If a member of the sales force submits
an entertainment expense (dinner cost for four) of $390, should
this expense be considered unusually high (and possibly worthy of
investigation by the company)? Explain your answer.
Yes
No
(d) Compute and interpret the z-score for
the following entertainment expenses. (Round
z-score calculations to 2 decimal places. Negative amounts should
be indicated by a minus sign.)