FAN

Use when

• forecasts that honestly show their spread
• committing to a range instead of a false point estimate

Do not use when

• fabricating bands the model never produced
• showing only the median (that is CH-TIM-01 with a dashed tail)

See instead

• no uncertainty statement exists: CH-TIM-01
• commitment vs plan is the story: CH-TIM-02

Alternatives

• CH-TIM-02 (progress vs plan, no uncertainty)
• CH-DST-10 (uncertainty on categories)

Rules

• bands are DECLARED quantiles; the source names the method
• median dashed: it is an estimate, not a measurement
• the forecast region is visibly divided from actuals
• y starts at zero

Never do this

• bands without a named method
• solid median implying certainty
• hiding the actual/forecast boundary

QA before delivering

• method in the source line
• band90 contains band50 contains median
• median dashed
• unit once
• source present

Data shape

{
  "title": "The forecast reaches 70 by October, inside a 22-point spread",
  "eyebrow": "PROGRESS FORECAST",
  "source": "Source: sample dataset v1; quantile forecast, monthly refit",
  "unit": "%",
  "x": [
    "Jan",
    "Feb",
    "Mar",
    "Apr",
    "May",
    "Jun",
    "Jul",
    "Aug",
    "Sep",
    "Oct"
  ],
  "split": 6,
  "actual": [
    40,
    44,
    47,
    52,
    55,
    58
  ],
  "median": [
    61,
    64,
    67,
    70
  ],
  "band50": [
    [
      59,
      63
    ],
    [
      61,
      67
    ],
    [
      63,
      71
    ],
    [
      65,
      75
    ]
  ],
  "band90": [
    [
      56,
      66
    ],
    [
      57,
      71
    ],
    [
      58,
      76
    ],
    [
      59,
      81
    ]
  ]
}