=+9. The number of contaminating particles on a silicon wafer prior to a certain rinsing process was determined for each wafer in a sample of size 100, resulting in the following frequencies:

Number of particles: 0 1 2 3 4 5 6 7 Frequency: 1 2 3 12 11 15 18 10 Number of particles: 8 9 10 11 12 13 14 Frequency: 12 4 5 3 1 2 1