| Value | Category | Cases | |
|---|---|---|---|
| -9 | Don't know (spontaneous) | 16 | 
                                    
                                    4.4%
                                 | 
| 1 | One hour or less | 113 | 
                                    
                                    31.1%
                                 | 
| 2 | 26 | 
                                    
                                    7.2%
                                 | |
| 3 | 13 | 
                                    
                                    3.6%
                                 | |
| 4 | 12 | 
                                    
                                    3.3%
                                 | |
| 5 | 4 | 
                                    
                                    1.1%
                                 | |
| 6 | 6 | 
                                    
                                    1.7%
                                 | |
| 7 | 2 | 
                                    
                                    0.6%
                                 | |
| 8 | 14 | 
                                    
                                    3.9%
                                 | |
| 9 | 1 | 
                                    
                                    0.3%
                                 | |
| 10 | 4 | 
                                    
                                    1.1%
                                 | |
| 12 | 11 | 
                                    
                                    3%
                                 | |
| 14 | 1 | 
                                    
                                    0.3%
                                 | |
| 15 | 2 | 
                                    
                                    0.6%
                                 | |
| 16 | 5 | 
                                    
                                    1.4%
                                 | |
| 20 | 1 | 
                                    
                                    0.3%
                                 | |
| 24 | 22 | 
                                    
                                    6.1%
                                 | |
| 28 | 4 | 
                                    
                                    1.1%
                                 | |
| 30 | 13 | 
                                    
                                    3.6%
                                 | |
| 32 | 3 | 
                                    
                                    0.8%
                                 | |
| 36 | 7 | 
                                    
                                    1.9%
                                 | |
| 40 | 15 | 
                                    
                                    4.1%
                                 | |
| 42 | 2 | 
                                    
                                    0.6%
                                 | |
| 44 | 1 | 
                                    
                                    0.3%
                                 | |
| 48 | 10 | 
                                    
                                    2.8%
                                 | |
| 54 | 1 | 
                                    
                                    0.3%
                                 | |
| 56 | 8 | 
                                    
                                    2.2%
                                 | |
| 60 | 6 | 
                                    
                                    1.7%
                                 | |
| 72 | 4 | 
                                    
                                    1.1%
                                 | |
| 75 | 1 | 
                                    
                                    0.3%
                                 | |
| 80 | 3 | 
                                    
                                    0.8%
                                 | |
| 96 | 2 | 
                                    
                                    0.6%
                                 | |
| 112 | 2 | 
                                    
                                    0.6%
                                 | |
| 120 | 7 | 
                                    
                                    1.9%
                                 | |
| 160 | 2 | 
                                    
                                    0.6%
                                 | |
| 168 | 1 | 
                                    
                                    0.3%
                                 | |
| 176 | 2 | 
                                    
                                    0.6%
                                 | |
| 180 | 1 | 
                                    
                                    0.3%
                                 | |
| 208 | 1 | 
                                    
                                    0.3%
                                 | |
| 240 | 8 | 
                                    
                                    2.2%
                                 | |
| 288 | 1 | 
                                    
                                    0.3%
                                 | |
| 400 | 1 | 
                                    
                                    0.3%
                                 | |
| 416 | 1 | 
                                    
                                    0.3%
                                 | |
| 480 | 1 | 
                                    
                                    0.3%
                                 | |
| 576 | 1 | 
                                    
                                    0.3%
                                 | |
| 720 | 1 | 
                                    
                                    0.3%
                                 |