Final answer:
A scatter diagram shows the relationship between two variables, indicating whether they have a strong or weak correlation and if the relationship is linear or curved.
Step-by-step explanation:
True, a scatter diagram can indeed show whether a pair of variables has a strong or weak relationship, and it can also indicate whether that relationship is linear or curved. A scatter plot displays the correlation between two variables: if the points are closely packed along a line, it indicates a strong linear relationship, either positive or negative. Conversely, if the points are widely scattered without any discernible pattern, this suggests a weak or no correlation between the variables.
If the relationship displayed on the scatter plot is close to a straight line, it reflects that the variables have a linear relationship, making them good candidates for linear regression. However, if the pattern is curved, the relationship may be better represented by a non-linear model. By examining a scatter plot, one can decide on the appropriateness of a linear model or the need for a more complex model to describe the relationship between two variables.