Contact arrives
       ↓
  Random assignment (50/50)
       ↓
    ┌──────┴──────┐
    ↓             ↓
 Variant A    Variant B
    ↓             ↓
   Track        Track
    ↓             ↓
  Analyze results
       ↓
  Implement winner

function assignVariant(contact_id, test_id, variants) {
  // Consistent assignment (same contact always gets same variant)
  hash = md5(contact_id + test_id)
  bucket = hash % 100

  cumulative = 0
  for (variant in variants) {
    cumulative += variant.percentage
    if (bucket < cumulative) {
      return variant.name
    }
  }
}

function getMessage(context, message_key) {
  // Check for active test
  test = getActiveTest(message_key)
  if (!test) {
    return getDefaultMessage(message_key)
  }

  // Get variant assignment
  variant = assignVariant(context.contact_id, test.id, test.variants)

  // Return variant message
  return test.variants[variant].message
}

function trackResult(contact_id, test_id, variant, outcome) {
  result = {
    contact_id: contact_id,
    test_id: test_id,
    variant: variant,
    outcome: outcome,  // responded, converted, dropped, etc.
    timestamp: now()
  }
  store(result)
  updateTestStats(test_id, variant, outcome)
}

function isSignificant(variant_a, variant_b, confidence=0.95) {
  // Calculate z-score
  p_a = variant_a.conversions / variant_a.impressions
  p_b = variant_b.conversions / variant_b.impressions
  p_pooled = (variant_a.conversions + variant_b.conversions) /
             (variant_a.impressions + variant_b.impressions)

  se = sqrt(p_pooled * (1 - p_pooled) *
            (1/variant_a.impressions + 1/variant_b.impressions))

  z = (p_b - p_a) / se

  // Check against critical value
  z_critical = 1.96  // for 95% confidence
  return abs(z) > z_critical
}

Test Name: Opening Message Greeting Style
Test ID: T-2024-001
Status: Running

Hypothesis:
A casual greeting will increase response rate because
it feels more human and less corporate.

Variants:
- Control (50%): "Hello! Thanks for reaching out..."
- Variant A (50%): "Hey there! Great to hear from you..."

Primary Metric: Response rate
Secondary Metrics: Sentiment, conversion rate
Sample Size Target: 1,000 per variant
Duration: 2 weeks or until significant

Results:
[To be completed]