Dr. Campbell takes time to discuss terms with the reader that are used later in the book. Specifically, he details definitions of: (1) a scientific law; (2) causation; and (3) correlation. His first example is a scientific law – a declaration that holds 100% of the time – such as gravity. Each time I drop a rock from a place above the earth, the rock will fall down toward the earth.
The second term, causation, refers to cause-and-effect, which is difficult and time-consuming to prove. The example of many studies showing smoking may cause lung cancer. But that example is not a law, as some people smoke and never contract lung cancer. And not all lung cancer is caused by smoking.
The next term, correlation, is an important first step toward proving causation. Correlation is found through statistical analysis of data. His example used the fact that countries with more telephone poles have been found to correlate with higher rate of heart disease. However, not many scientists believe that telephone pole counts causes heart disease. With closer examination, the increased number of telephone pole may be an indicator of something else that may contribute to heart disease (income level for example).
Dr. Campbell points out that higher correlation using statistical significance allows scientists to state that certain conclusions found are greater than chance happenings. Consider flipping a fair coin. If you flip a coin three times and the coin lands as heads each time, it could be chance. However, if you flip a coin one hundred times and the coin lands on heads 100 times, either the coin is not fair or both sides are heads.
A result is statistically significant when it is found that less than 5% probability the result is due to chance. In other words, the same result occurs when the conditions are repeated 95% of the time. Notice that a scientific law is 100% of the time. Statistical significance is used to help determine correlations.
A scientific perspective is added in biological relationship. Returning to the number of telephone pole and incidence of heart disease, there is no biological relationship between the two events. However, research can demonstrate relationships between protein intake and liver cancer. This is called mechanisms of action and strengthens reliability of correlation.
The final research term is metanalysis. Meta refers to many and accurately describes what many analysis is: metanalysis. Individual data sets from different studies are combined and analyzed as one set. Due to the combination of numbers, metanalysis results are more substantial than individual studies.
Note that the process of any study may not result in an absolute 100% scientific law such as gravity, but using the results of research with common sense provides insight to choices within your life.