The right chart makes insights obvious. The wrong chart confuses people. Here's how to choose:

Start With Your Goal

1. Comparing Values → Bar Chart

Use when: Comparing quantities across categories

Examples: Sales by region, revenue by product, count by department

Why it works: Humans easily compare bar lengths

✅ Good: Horizontal bar chart (easier to read long labels)
❌ Avoid: 3D bars, too many categories (>15)

2. Showing Trends Over Time → Line Chart

Use when: Continuous data over time periods

Examples: Revenue over months, website traffic over days, stock prices

Why it works: Shows direction and rate of change clearly

✅ Good: Start Y-axis at 0 for honest representation
❌ Avoid: Too many lines (>5 gets messy)

3. Showing Proportions → Pie Chart (Use Sparingly!)

Use when: Parts of a whole (must add to 100%)

Examples: Market share, budget breakdown by category

Limitations:

• Only use for 2-5 categories max
• Humans are bad at comparing angles
• Often a bar chart is better!

✅ Good: 3 clear segments
❌ Avoid: 10+ tiny slices, 3D pie charts, exploded slices

4. Showing Distribution → Histogram or Box Plot

Histogram: See shape of distribution

Box plot: See median, quartiles, outliers

Examples: Age distribution, salary ranges, test scores

Histogram: Shows if data is normal, skewed, bimodal
Box plot: Great for comparing distributions across groups

5. Showing Relationships → Scatter Plot

Use when: Exploring correlation between two variables

Examples: Price vs sales, age vs income, ad spend vs revenue

Why it works: Reveals patterns, clusters, outliers

✅ Add trendline to show correlation
✅ Color points by category for extra dimension

6. Showing Part-to-Whole Over Time → Stacked Area Chart

Use when: Multiple categories summing to a total, over time

Examples: Revenue by product line over years, traffic sources over months

Warning: Hard to compare middle segments. Only use for general trends.

Quick Decision Tree

Your Question	Chart Type
How do categories compare?	Bar chart
How has this changed over time?	Line chart
What's the breakdown?	Pie chart (2-5 items) or Bar chart
What's the distribution?	Histogram or Box plot
Is there a relationship?	Scatter plot
How do parts change over time?	Stacked area chart
Where are the outliers?	Box plot or Scatter plot

Common Mistakes to Avoid

• ❌ Pie chart with 10+ slices → Use bar chart instead
• ❌ 3D charts → Distort perception, use 2D
• ❌ Dual Y-axes → Can mislead, use with caution
• ❌ Too many colors → Stick to 5-7 max
• ❌ Not labeling axes → Always include units!
• ❌ Misleading Y-axis scales → Start at 0 for bar charts

The "When in Doubt" Rule

Can't decide? Use a bar chart. It's:

• ✅ Easy to understand
• ✅ Works for most comparisons
• ✅ Harder to mess up than pie charts
• ✅ Accessible (colorblind-friendly if properly designed)

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