Solutions:

A. Correlation coefficient

Correlation coefficient is the value that gives a statistical relationship between two given variables, or in other words a value that quantifies the type of relationship that exist between any two given variables.

B. Scatter plot

This is a diagram/graph that demonstrates the relationship that exists between two sets of data. The set of data contained in the scatter plot can be used to get a mathematical correlation between two variables. A scatter plot can also be used to demonstrate nonlinear relationship between two variables., This can be done by fitting a line in the plotted data. The scatter plot can be used to suggest various types of correlations and also the confidence intervals. Both continuous variables can be used in a scatter plot.

C. Bivariate relationship

Bivariate relationship means an analysis that is used to find out the relationship between exact two variables. Bivariate relationship is helpful when determining the simple hypothesis test of association.

2. Identify when to use the Pearson r.

Pearson r is used when one is need of determining the strength and direction of a linear relationship that exist between two given variables. In most cases Pearson moment correlation is abbreviated as r which ranges from -1 to +1, If r = -1, then there exist a negative relationship, if r = 0, then there is no relationship and if r= +1, then there exist a positive perfect relationship between given variables.

3. Identify when to use Spearman's rho.

This is a type of rank correlation that is used when one wishes to determine/measure the degree(how well) the correlation/relationship between two variables in which it can be described by the use of a monotonic function.

It is given by: r = 1 - [6∑d²/ n(n²-1)]