Two variables can be plotted together in -: (A) Pie cha, (B) Histogram, (C) Frequency polygon, (D) Scatter diagram
Answer is D. - scatter maps show the relationship between two variables - if dots cluster round a straight line, it shows evidence of relationship of a linear nature. If there is no such cluster, it is probable that there is no relationship between the variables. Reference : Park's textbook of preventive and social medicine, 23rd edition, pg no:847