Through both diagrams and graphs are handy tools in the hands of a statistician for representation of statistical data, there are much differences between the two. The chief points of difference between them may be outlined as under:
(i) Diagrams are very attractive to eyes and hence, they are invariably used in advertisement and publicity. But graphs are not attractive to eyes and hence, generally, they are not used in advertisement and publicity.
(ii) Diagrams do not add anything to the meaning of the data and hence, they cannot be used by statisticians or research scholars in the further analysis of data. But graphs make the data more meaningful and hence, they are very much used by statisticians and research scholars in the analysis and interpretation of data.
(iii) Diagrams create effective and long lasting impression in the minds of the onlookers but graphs do not create such impression.
(iv) Diagrams help us in making comparison between the data but graphs help us in studying the cause and effect relationship between two variables.
(v) Diagrams are better drawn on plain papers but graphs are accurately drawn on graph papers.
(vi) Diagrams are rarely used to present frequency distributions. But graphs are mostly used to present such distributions.
(vii) Diagrams never present any mathematical relationship between the variables. But graphs always present mathematical relationship between the variables.