Final answer:
In the described correlational study, as blood pressure increases, aggression also increases, hence this represents a positive correlation. The correlation coefficient for a positive correlation ranges from 0 to 1, indicating a direct relationship between the variables.
Step-by-step explanation:
When a correlational study finds that as one variable increases, so does another, we are looking at a positive correlation. In this case, the scenario described shows that as blood pressure increases, aggression levels also increase. This indicates that these two variables move in the same direction, which by definition, signifies a positive correlation.
It's important to note that a correlation coefficient, usually represented by the letter r, is used to describe the strength and direction of the relationship between two variables. For positive correlations, the correlation coefficient is between 0 and 1. Conversely, in a negative correlation, as one variable increases, the other decreases, and the correlation coefficient will be between -1 and 0.
Therefore, the correct answer to the given question is (a) positive correlation. A negative correlation, spurious correlation, or inverse correlation would not fit the description of the relationship between blood pressure and aggression as stated.