Here are the number of pieces of mail received at a school office for 36 days.
| 123 |
70 |
90 |
| 80 |
78 |
72 |
| 52 |
103 |
138 |
| 112 |
92 |
93 |
| 118 |
118 |
106 |
| 95 |
131 |
59 |
| 151 |
115 |
97 |
| 100 |
128 |
130 |
| 66 |
135 |
76 |
| 143 |
100 |
88 |
| 110 |
75 |
60 |
| 115 |
105 |
85 |
a) Plot these data.
b) Find appropriate summary statistics.
c) Write a brief description of the school's mail deliveries.
d) What percent of the days actually lie within one standard deviation of the mean? Comment.