Which of the following statements are true with respect to ‘Data handling’ ?

The correct option is:
A graphical representation of data is easier to understand when there is a trend or comparison to be shown.

Let us analyze each statement to understand why this statement is true and why the others are incorrect:

1. "A line graph is used to show comparison among categories of data."
This statement is incorrect. A line graph is primarily used to display data that changes continuously over time (trends over time). Comparison among discrete categories of data is best shown using a bar graph.

2. "A histogram is used to compare the parts of a whole."
This statement is incorrect. A pie chart (or circle graph) is used to compare parts of a whole relative to the total. A histogram is used to show data divided into continuous class intervals (ranges of numerical values).

3. "A graphical representation of data is easier to understand when there is a trend or comparison to be shown."
This statement is correct. Visual tools such as bar graphs, line graphs, and pie charts summarize complex raw data into visual patterns, making comparisons, patterns, and trends far easier and faster to comprehend than looking at raw numbers in a table.

4. "A bar graph displays data that changes continuously over periods of time."
This statement is incorrect. Data that changes continuously over periods of time is displayed using a line graph. Bar graphs are used to compare distinct categories of discrete data.

Therefore, the third statement is the only true statement regarding data handling.