This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Dental
A statistical test which indicates the chance or probability of an observed difference between two means occurring by chance is called, 
Select and explain. 
A. Tests of significance, B. Means, C. Ratio, D. Normalcy
A: Tests of significance
Answer: A: Tests of significance 
Explanation: None