keeping notes on the condition of equipment used in the procedure conducting an investigation with a group of people conducting the procedure thoroughly one time repeating an investigation several times
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which procedure best helps to determine whether an investigation is scientifically valid?
Possibilities:
- keeping notes on the condition of equipment used in the procedure
- conducting an investigation with a group of people
- conducting the procedure thoroughly one time
- repeating an investigation several times

repeating an investigation several times