Scatter plot very clearly helps us to identify the association between two variables, which is explanatory variable and response variable. If we want to show the relationship between two given sets then we can use the scatter plot. We can create the scatter plot by using ordered pairs of given sets in a Cartesian coordinate system. This is a way to show the correlation between bivariate data. In this plot, first variable lies on xaxis(horizontal axis) and the second variable lies on yaxis(vertical axis).
If the data points make a straight line going from the
origin out to high x and yvalues, then the variables
are said to be positively correlated. If
the line goes from a highvalue on the yaxis down to
a highvalue on the xaxis then the variables are negatively correlated.
Perfect positive and perfect negative correlation lies in the range of (1, +1). If the value is Zero then we say there is no correlation among the variables.
Given below is the table which helps you in understanding the relationship between two variables and their association.
Less than 0.2

Very weak relationship 
0.20.4 
Weak Relationship 
0.40.6 
Moderate Relationship 
0.60.8 
Strong Relationship 
Greater than 0.8 
Very strong Relationship 
If there is no relation between the sets A and B, then scatter graph shows no trend.
To know about the trend, we draw the line of best fit. If the slope of the line is positive then we say there is a positive trend between the sets and if the slope of the line is negative then the trend is said to be negative.