This is why it is better to take three measurements and do an average every time to minimize errors. The studies on correlation probably have a large enough sa

This is why it is better to take three measurements and do an average every time to minimize errors. The studies on correlation probably have a large enough sample size to become statistically significant - i.e. you have to read the "Method" section to find out how reliable it is, this requires certain kind of statistics and/or scientific background.