How do you decide which chart to use for a piece of data?
What the interviewer wants to hear
- Start from the question or message
- Line for trends over time
- Bar for comparing categories
- Scatter for relationships between two numbers
- Avoid pie charts with many slices and 3D effects
Model answer
I start from the question I want the chart to answer, not from the data. If the question is "how has this changed over time", I use a line chart. If it is "which category is biggest", I use a bar chart, usually sorted, and horizontal if labels are long. To show the relationship between two numbers, like ad spend and sales, I use a scatter plot. For distribution I use a histogram or box plot. I only use a pie chart for parts of a whole with two or three slices; otherwise bars are easier to compare. I avoid 3D and too many colours, use one highlight colour for the key point, label axes clearly, and put the takeaway in the title, for example "Sales fell 12% in March" instead of just "Sales".
Can you answer it under time pressure?
Take a timed easy round and get scored on every answer.
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