A Power BI report includes a bar chart showing total sales by product category. The report designer wants to add a trend line to the chart to show the overall sales trend over time. Which type of visual should be used instead?
A line chart encodes data points along a continuous time axis and connects them with straight lines, allowing the eye to perceive direction, rate of change, and periodicity. Because the x-axis is continuous and time-ordered, Power BI can compute and overlay a trend line using linear regression, moving average, or other built-in analytics in the Analytics pane. It is the default and recommended visual for time-series trend analysis because it preserves the sequential structure of the data.
Why this answer
A line chart is the correct visual to show a trend over time because it plots data points connected by straight lines, making it easy to see the overall direction and pattern of total sales across a continuous time axis. Bar charts, including stacked variants, are designed for comparing discrete categories, not for displaying continuous trends.
Exam trap
The trap here is that candidates may think a bar chart with a trend line added via the analytics pane is acceptable, but the question asks which visual should be used instead, implying the bar chart is not the optimal choice for showing a trend over time.
How to eliminate wrong answers
Option A is wrong because a stacked bar chart is used to show the composition of a total across categories over time or groups, not to display a single trend line for total sales. Option C is wrong because a scatter chart is used to show the relationship between two numerical variables, not to display a single metric's trend over time. Option D is wrong because a pie chart shows proportions of a whole at a single point in time and cannot represent trends over time.