Graphical presentation of data

• Used for Qualitative data to compare mutually exclusive categories of one variable.

• Used for Qualitative data to compare mutually exclusive categories of two or more variables.

• Used for Qualitative data to compare mutually exclusive categories of two or more variables.

• Used for Qualitative data to compare mutually exclusive categories of one variable.

• Used for Qualitative data to show the degree of overlap and exclusive data in one or two categories.

• Used for Qualitative data especially for the lay population where data is presented in form of pictures.

On a map of locality, the distribution of cases is represented. Widely used in epidemic investigations.

Area map used to compare the disease or event occurence in different localities. The areas are shaded in different colours to represent the occurence of the disease or event magnitude. Disease or event occurence should be calculated as rate and then marked on the map with different colour shades rather than using absolute numbers. 

Error bars represent the variability of data and indicate the error or uncertainity in the data measured. Error bars represent one standard deviation or one standard error.

In the graph on sex wise distribution of cancer cases shown below the error bar represents one standard deviation.

• Used for Quantitative data that is of continuous type.

• The x-axis has the continuous variable data that is categorised into equal class intervals.

• The y-axis represents the frequency.

• The frequency of the data is plotted on y axis against the class intervals.

When the midpoints of the bars of histogram are joined by a line it is called as frequency polygon

When there is a huge data set of quantitative continuous data,  and the class intervals are narrow, the frequency polygon loses its angulation and appears as a smooth curve.

• A type of histogram, where the x axis has the time interval. 

• Used for reporting disease frequency in an outbreak/epidemic.

• Used to represent time trend of data.

• X-axis has the time plotted on it.

• Y-axis has the frequency of data.

• Plotted usings dots and then joining the dots.

• Cumulative frequency of data are plotted against the upper limit of that class interval.

• Example - To show the total number of cases seen in the year or the period under the study, the number of cases reported monthly can be presented using cumulative frequency

• Useful to show the relationship between two continuous variables.

• Relationship between the two variables can be observed.

• The scatter diagram below show positive relationship between age and random blood glucose levels. As the age increases, the blood glucose levels are also increasing.

• The scatter diagram below show negative relationship between exam scores and time spent on social media. As the time spent on the social media decreases, the exam scores increases.

• The scatter diagram below does not show any relationship between serum cholesterol and glucose levels.

The data range and quartiles(25%, 50% and 75%) can be represented using box and whisker plot. this is useful when two data sets of quantitative variable need to be compared.

• It is an histogram where the age and sex distribution of a population is plotted.

• The shape of the pyramid / histogram varies for developed and developing countries.