Descriptive
Statistics of U.S. traffic Fatalities occurring on Interstates and
Non-interstates at various speeds ( File P2_43.xls)
|
|
ISO55 |
ISA55 |
NIS55 |
NIS50 |
NIS45 |
NIS40 |
NIS35 |
NISLT
35 |
Mean |
16.76 |
13.41 |
110.08 |
10.16 |
26.84 |
14.29 |
27.55 |
28.04 |
|
Standard Error |
3.12 |
3.45 |
19.76 |
1.79 |
4.88 |
2.95 |
5.12 |
4.68 |
|
Median |
12 |
7 |
59 |
7 |
14 |
7 |
16 |
16 |
|
Mode |
0 |
0 |
5 |
3 |
5 |
3 |
3 |
20 |
|
Standard Deviation |
22.27 |
24.63 |
141.15 |
12.80 |
34.83 |
21.05 |
36.54 |
33.42 |
|
Sample Variance |
495.82 |
606.73 |
19922.07 |
163.93 |
1213.25 |
443.21 |
1335.33 |
1116.84 |
|
Kurtosis |
11.12 |
19.85 |
7.76 |
14.19 |
2.44 |
8.47 |
12.51 |
4.70 |
|
Skewness |
3.04 |
4.22 |
2.52 |
3.27 |
1.80 |
2.72 |
3.08 |
2.24 |
|
Range |
115 |
147 |
678 |
76 |
141 |
109 |
211 |
150 |
|
Minimum |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
0 |
|
Maximum |
115 |
147 |
678 |
76 |
141 |
109 |
211 |
150 |
|
Sum |
855 |
684 |
5614 |
518 |
1369 |
729 |
1405 |
1430 |
|
Count |
51 |
51 |
51 |
51 |
51 |
51 |
51 |
51 |
ISO55-
Interstate Over 55 mph
ISA55 - Interstate at 55 mph
NIS55 - Non
Interstate at 55 mph
NIS50 - Non
Interstate at 50 mph
NIS45 - Non
Interstate at 45 mph
NIS40 - Non
Interstate at 40 mph
NIS35 - Non
Interstate at 35 mph
NISLT
35 - Non Interstate under 35 mph
Fatalities on Interstates
Based on
the Mean – Number of fatalities on the interstate at speeds above 55 mph is
more. (16.76 > 13.41)
However, it
can be observed that the Variance is higher for lower speeds.
Fatalities
on Non-Interstates
Even though, the number of fatalities goes down as speeds
increase beyond 35 mph it can be observed that number of fatalities is
alarmingly high at 55mph. At speeds above 35mph and less than 55mph it is difficult
to generalize the statement that with an increase in speed the number of
fatalities goes down.
From the Variance & the Mean charts we can say that the
probability of fatalities occurring on Non-Interstate is much higher at 55 mph.
Fatalities
at 55 mph
|
|
Mean |
Mean |
Variance |
|
Interstate |
13.41 |
10.86% |
606.73 |
|
Non
Interstate |
110.08 |
89.14% |
19922.07 |
It can be clearly observed that approximately 90% of fatalities occurring at 55 mph do so on
Non-Interstates.
Combination
of speed and road types
|
Speed |
Mean |
Variance |
ISO55
|
16.76 |
495.82 |
|
ISA55 |
13.41 |
606.73 |
|
NIS55 |
110.08 |
19922.07 |
|
NIS50 |
10.16 |
163.93 |
|
NIS45 |
26.84 |
1213.25 |
|
NIS40 |
14.29 |
443.21 |
|
NIS35 |
27.55 |
1335.33 |
|
NISLT
35 |
28.04 |
1116.84 |
The most lethal combination for fatalities
is driving at 55mph on Non- Interstates.
The safest combination is driving at 50 mph
on Non-Interstates.