diff --git a/src/Drush/Commands/RlCommands.php b/src/Drush/Commands/RlCommands.php
index 9b3d0b5..156e879 100644
--- a/src/Drush/Commands/RlCommands.php
+++ b/src/Drush/Commands/RlCommands.php
@@ -89,7 +89,13 @@ public function listExperiments(): RowsOfFields {
   #[CLI\Usage(name: 'drush rl:status ab_test_button_color', description: 'Get status of button color test')]
   #[CLI\Usage(name: 'drush rl:status ai_sorting-help_center_categories-block_1 --format=json', description: 'Get detailed status as JSON')]
   public function status(string $experimentId, array $options = ['format' => 'yaml']): array {
-    return $this->analyzer->getStatus($experimentId);
+    try {
+      return $this->analyzer->getStatus($experimentId);
+    }
+    catch (\InvalidArgumentException $e) {
+      $this->logger()->error($e->getMessage());
+      throw $e;
+    }
   }
 
   /**
@@ -130,12 +136,18 @@ public function status(string $experimentId, array $options = ['format' => 'yaml
   #[CLI\Usage(name: 'drush rl:perf ai_sorting-help_center_categories-block_1 --limit=10 --format=json', description: 'Get top 10 performers as JSON')]
   #[CLI\Usage(name: 'drush rl:perf ab_test_headline_variants --sort=impressions', description: 'Sort by traffic volume')]
   public function performance(string $experimentId, array $options = ['limit' => 20, 'sort' => 'rate']): RowsOfFields {
-    $data = $this->analyzer->getPerformance(
-      $experimentId,
-      (int) $options['limit'],
-      $options['sort']
-    );
-    return new RowsOfFields($data['arms']);
+    try {
+      $data = $this->analyzer->getPerformance(
+        $experimentId,
+        (int) $options['limit'],
+        $options['sort']
+      );
+      return new RowsOfFields($data['arms']);
+    }
+    catch (\InvalidArgumentException $e) {
+      $this->logger()->error($e->getMessage());
+      throw $e;
+    }
   }
 
   /**
@@ -166,12 +178,18 @@ public function performance(string $experimentId, array $options = ['limit' => 2
   #[CLI\Usage(name: 'drush rl:trends ab_test_headline_variants', description: 'Get weekly trends')]
   #[CLI\Usage(name: 'drush rl:trends mock_10_arm_test --period=daily --periods=14 --format=json', description: 'Get 14 days of daily data')]
   public function trends(string $experimentId, array $options = ['period' => 'weekly', 'periods' => 8]): RowsOfFields {
-    $data = $this->analyzer->getTrends(
-      $experimentId,
-      $options['period'],
-      (int) $options['periods']
-    );
-    return new RowsOfFields($data['data']);
+    try {
+      $data = $this->analyzer->getTrends(
+        $experimentId,
+        $options['period'],
+        (int) $options['periods']
+      );
+      return new RowsOfFields($data['data']);
+    }
+    catch (\InvalidArgumentException $e) {
+      $this->logger()->error($e->getMessage());
+      throw $e;
+    }
   }
 
   /**
@@ -195,10 +213,16 @@ public function trends(string $experimentId, array $options = ['period' => 'week
   #[CLI\Usage(name: 'drush rl:export ab_test_button_color', description: 'Export experiment data as JSON')]
   #[CLI\Usage(name: 'drush rl:export mock_10_arm_test --snapshots > export.json', description: 'Export with snapshots to file')]
   public function export(string $experimentId, array $options = ['snapshots' => FALSE, 'format' => 'json']): array {
-    return $this->analyzer->export(
-      $experimentId,
-      (bool) $options['snapshots']
-    );
+    try {
+      return $this->analyzer->export(
+        $experimentId,
+        (bool) $options['snapshots']
+      );
+    }
+    catch (\InvalidArgumentException $e) {
+      $this->logger()->error($e->getMessage());
+      throw $e;
+    }
   }
 
   /**
@@ -221,18 +245,24 @@ public function export(string $experimentId, array $options = ['snapshots' => FA
   #[CLI\Usage(name: 'drush rl:analyze ab_test_button_color', description: 'Get full analysis with recommendations')]
   #[CLI\Usage(name: 'drush rl:analyze mock_10_arm_test --format=json', description: 'Get analysis as JSON')]
   public function analyze(string $experimentId, array $options = ['format' => 'yaml']): array {
-    $status = $this->analyzer->getStatus($experimentId);
-    $performance = $this->analyzer->getPerformance($experimentId, 10);
+    try {
+      $status = $this->analyzer->getStatus($experimentId);
+      $performance = $this->analyzer->getPerformance($experimentId, 10);
 
-    return [
-      'experiment' => $status['experiment'],
-      'status' => $status['status'],
-      'summary' => $status['summary'],
-      'value_generated' => $status['value_generated'],
-      'top_performers' => array_slice($performance['arms'], 0, 5),
-      'insights' => $performance['insights'],
-      'recommendation' => $this->generateRecommendation($status, $performance),
-    ];
+      return [
+        'experiment' => $status['experiment'],
+        'status' => $status['status'],
+        'summary' => $status['summary'],
+        'value_generated' => $status['value_generated'],
+        'top_performers' => array_slice($performance['arms'], 0, 5),
+        'insights' => $performance['insights'],
+        'recommendation' => $this->generateRecommendation($status, $performance),
+      ];
+    }
+    catch (\InvalidArgumentException $e) {
+      $this->logger()->error($e->getMessage());
+      throw $e;
+    }
   }
 
   /**
diff --git a/src/Service/RlAnalyzer.php b/src/Service/RlAnalyzer.php
index 6c2798b..1974322 100644
--- a/src/Service/RlAnalyzer.php
+++ b/src/Service/RlAnalyzer.php
@@ -299,9 +299,6 @@ public function getTrends(string $experimentId, string $period = 'weekly', int $
       $trendDirection = 'declining';
     }
 
-    $firstRate = $data[0]['rate'];
-    $lastRate = end($data)['rate'];
-
     return [
       'experiment_id' => $experimentId,
       'period' => $period,
@@ -309,10 +306,10 @@ public function getTrends(string $experimentId, string $period = 'weekly', int $
       'data' => $data,
       'analysis' => [
         'trend_direction' => $trendDirection,
-        'first_period_rate' => $firstRate,
-        'last_period_rate' => $lastRate,
+        'first_period_rate' => $data[0]['rate'] ?? 0,
+        'last_period_rate' => end($data)['rate'] ?? 0,
         'overall_change_pct' => count($data) >= 2
-          ? round(($lastRate - $firstRate) * 100 / max(0.01, $firstRate), 1)
+          ? round((end($data)['rate'] - $data[0]['rate']) * 100 / max(0.01, $data[0]['rate']), 1)
           : 0,
       ],
     ];
@@ -674,6 +671,7 @@ protected function estimateConfidence(int $conversions, int $impressions): float
     $p = $conversions / $impressions;
     $z = 1.96;
     $denominator = 1 + $z * $z / $impressions;
+    $center = ($p + $z * $z / (2 * $impressions)) / $denominator;
     $spread = $z * sqrt(($p * (1 - $p) + $z * $z / (4 * $impressions)) / $impressions) / $denominator;
 
     // Narrower interval = higher confidence.