Americium (atomic number 95) is a synthetic element that is produced as a byproduct in certain nuclear reactions. It was first produced by Glenn Seaborg and his colleagues at the University of California, Berkeley. The isotope americium-241 now has commercial applications in the ionization chambers of smoke detectors. It decays by emission of alpha particles and has a half-life of 432.2 years.
In 1966, the statistician J. Berkson studied alpha particle emissions from a sample of americium-241. The table below is a frequency distribution for the number of emissions in 1207 ten-second intervals, and is adapted from data in Rice.
| N | Freq |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 13 |
| 3 | 28 |
| 4 | 56 |
| 5 | 105 |
| 6 | 126 |
| 7 | 146 |
| 8 | 164 |
| 9 | 161 |
| 10 | 123 |
| 11 | 101 |
| 12 | 74 |
| 13 | 53 |
| 14 | 23 |
| 15 | 15 |
| 16 | 9 |
| 17 | 3 |
| 18 | 1 |
| 19 | 1 |