HISTOGRAM

Use when

• showing the shape of one distribution: skew, mode, outliers
• first look at any new numeric measure

Do not use when

• comparing several distributions (CH-DST-04 or CH-DST-09)
• categorical counts (CH-RNK-01; bins must be numeric intervals)

See instead

• the question is what share clears a threshold: CH-DST-06
• comparing shapes across groups: CH-DST-09

Alternatives

• CH-DST-06 (service-level reading)
• CH-DST-09 (smooth shape)

Rules

• bars touch: 1px seam only, the variable is continuous
• equal bin widths, edges labeled at the boundaries, not centers
• counts on the y axis start at zero

Never do this

• gaps between bars
• unequal bins without width-proportional areas
• labeling bin centers
• more than 20 bins

QA before delivering

• bars contiguous
• edges ascending and labeled
• y starts at zero
• unit once
• source present

Data shape

{
  "title": "Two thirds of lots clear customs within 15 days",
  "eyebrow": "CLEARANCE TIME",
  "source": "Source: customs log, H1",
  "unit": "lots",
  "edges": [
    0,
    5,
    10,
    15,
    20,
    25,
    30,
    35,
    40
  ],
  "counts": [
    18,
    42,
    31,
    17,
    9,
    5,
    3,
    1
  ]
}