What is the minimum concentration of solution to kill all bacteria in our hands?

[Sample excerpts]

Based on the raw data, I calculated the average and total number of bacteria in Petri dish. Below shows steps of several calculations I’ve done for this table.

• Calculation 1: Finding total numbers of bacteria in each Petri dish per experimentSum up the number of each colored bacteria for each experimentExample) For the first trial on the 0ml solution
  Number of red bacteria + yellow bacteria + green bacteria 10 + 4 + 4 = 18.0