Scientific investigation is usually carried out to explain and give answers to natural phenomenon. Now, this scientific investigation is performed through the three main types as described in the question.
With that being said, the most common parts of all types of investigation are :
1. Scientific question: In this stage, questions are usually asked on the basis of observation made which could be answered.
2. Procedure: In this stage, the dimension of the steps are followed to answer and test the scientific question.
3. Conclusion: This is the primary aim that we check when done with our sample values
