Visualizing Variability : Lists and Tables
The table below gives failure times in hours for a 107 electronic components. The raw data comes as an unordered list, which gives few clues about any pattern in the time to failure.
The sorted (ordered) list below shows that the time to failure runs from as little as 1 hour up to 129.9 hours. A close inspection might reveal are a lot of short times. However, it is still difficult to detect a pattern even in a sorted list. Sorting is a simple but useful technique. The next section demonstrates how charts can reveal patterns hidden in lists. The chart in figure 1 shows patterns in the data.
1.0
4.6
8.7
19.2
43.7
64.6
88.4
105.0
121.0
1.2
4.7
9.2
28.1
44.5
65.3
89.9
105.8
122.9
1.3
4.8
9.8
28.2
50.4
66.2
90.8
106.5
123.3
2.0
5.2
10.2
29.0
51.2
70.1
91.1
110.7
124.5
2.4
5.4
10.4
29.9
52.0
71.0
91.5
112.6
125.8
2.9
5.9
11.9
30.6
53.3
75.1
92.1
113.5
126.6
3.0
6.4
13.8
32.4
54.2
75.6
97.9
114.8
127.7
3.1
6.8
14.4
33.0
55.6
78.4
100.8
115.1
128.4
3.3
6.9
15.6
35.3
56.4
79.2
102.6
117.4
129.2
3.5
7.2
16.2
36.1
58.3
84.1
103.2
118.3
129.5
3.8
7.9
17.0
40.1
60.2
86.0
104.0
119.7
129.9
4.3
8.3
17.5
42.8
63.7
87.9
104.3
120.6
Figure 1. Bar chart of time to failure. Frequency is the number of parts that failed in each time class.