Final answer:
A major disadvantage of correlational studies is that they cannot demonstrate causation. Correlation indicates a relationship between variables but does not prove one causes the other.
Step-by-step explanation:
A major disadvantage of a correlational study is that it cannot establish causal relationships between variables. Correlation simply means that two variables are related in some way, positive or negative correlation, but does not prove that one causes the other. For example, observational studies might show that smoking is correlated with lung cancer, but without controlling all variables, we cannot conclude that smoking causes cancer, as there might be confounding factors at play.
Similarly, although a positive correlation between two variables means they change in the same direction, and a negative correlation means they change in opposite directions, this is not definitive proof of causation. Experiments, on the other hand, involve the manipulation and control of variables, which can help establish causal connections. Oftentimes, the misconception of correlation for causation can be spread by media reports, leading to misinformation.