In: Finance
The following data represent the 2019 monthly sales in units for the Pacific Region Sales Team of QualCase, Inc.
Month |
Units sold (xi) |
(x – x-bar) |
Squared values |
Divide total by n-1 |
SQRT |
Jan |
73 |
| |
| |
||
Feb |
79 |
| |
| |
||
Mar |
76 |
| |
| |
||
Apr |
79 |
| |
| |
||
May |
80 |
| |
| |
||
Jun |
78 |
| |
| |
||
Jul |
77 |
| |
| |
||
Aug |
78 |
| |
| |
||
Sep |
75 |
| |
| |
||
Oct |
72 |
| |
| |
||
Nov |
75 |
| |
| |
||
Dec |
82 |
V |
V |
||
TOTAL => |
TOTAL => |
||||
n = |
|||||
x-bar = |
PROBLEM #1: Use the table above and the procedures learned in class to calculate the standard deviation (notated as s) of average monthly sales. What is the standard deviation of average monthly sales?
PROBLEM #2: Apply the results of your answer to Problem #1 and use the table below and the procedures learned in class to calculate the 95% confidence interval for average monthly sales in units. What is the 95% confidence interval (CI) for average monthly sales?
SE of mean |
|
z-value |
1.96 |
Plus/minus value |
|
Upper CI value |
|
Lower CI value |
Answer 1:
Standard deviation of average monthly sales = 2.92
Calculations are as below (format as given is used):
The above excel with 'show formula' is given below:
Answer 2:
As calculated in answer 1 SD of mean monthly sales = 2.92
Plus/minus value = 2.92 * 1.96 = 5.73
Upper CI Valu = 77 + 5.73 = 82.73
Lower CI value = 77 - 5.73 = 71.27