Name: left and right truncation in survival data
Uploaded: 2025-01-09T15:14:17.000Z
Duration: 1 min 9 s
Channel: JoVE

في تحليل البقاء على قيد الحياة ، يتم قياس الوقت من بداية الدراسة ، مما يضمن مراقبة جميع المشاركين من وقت الصفر حتى وفاتهم أو تعرضهم للرقابة. لكن هذا ليس ممكنا دائما.
على سبيل المثال ، في دراسة تبحث في التعرض المهني لمادة مسرطنة محتملة ، قد يتم إجراء مقابلات مع عمال المصانع حول تعرضهم السابق وعوامل الخطر مثل السرطان ثم متابعتهم.
من الناحية المثالية ، الوقت صفر هو تاريخ بدء التوظيف وليس وقت بدء الدراسة.
لكن العمال الذين غادروا المصنع قبل بدء الدراسة لم يتم تضمينهم في الدراسة. تعرف هذه المشكلة باسم اقتطاع اليسار.
من ناحية أخرى ، يحدث اقتطاع الحق عندما يتم استبعاد الأفراد إذا تجاوز وقت الحدث الخاص بهم قيمة معينة ، مثل فترة الدراسة.
يختلف الاقتطاع عن الرقابة. وفي حالة الاقتطاع لا تتوافر معلومات عن بعض المواضيع لأنها مستبعدة من البيانات. من ناحية أخرى ، توفر الرقابة معلومات جزئية عن مثل هذه المواضيع.

الحذف في تحليل البقاء

Truncation in Survival Analysis

<div style="direction:rtl">يشير الحذف في تحليل البقاء إلى استبعاد الأفراد أو الأحداث من مجموعة البيانات استنادًا إلى معايير محددة تتعلق بوقت وقوع الحدث. يمكن أن يحدث هذا الاستبعاد في شكلين أساسيين: الحذف الأيسر والحذف الأيمن. يحدث الحذف الأيسر عندما يتم استبعاد الأفراد الذين شهدوا الحدث محل الاهتمام قبل وقت معين في الدراسة. غالبًا ما يكون هذا بسبب "الدخول المتأخر" إلى الدراسة حيث يتم ملاحظة أولئك الذين نجوا حتى نقطة دخول معينة فقط. على سبيل المثال، في دراسة مهنية، لن يكون العمال الذين تقاعدوا أو ماتوا قبل بدء الدراسة جزءًا من مجموعة البيانات، مما يؤدي إلى تحيز يشمل فقط أولئك الذين ما زالوا معرضين للخطر بعد نقطة الدخول. الحذف الأيمن أقل شيوعًا ويحدث عندما يتم تضمين الأفراد الذين شهدوا الحدث بحلول وقت معين فقط. يمكن أن يحدث هذا في الدراسات التي حدث فيها الحدث بالفعل، ويتم النظر فقط في أولئك الذين لديهم نتائج ملحوظة. ومن الأمثلة على ذلك دراسة الوفيات حيث يتم تسجيل الوفيات ضمن إطار زمني محدد فقط، مع استبعاد أولئك الذين عاشوا بعد فترة المراقبة. يقع الفرق بين الحذف والرقابة في توفر البيانات. يحدث الحذف عندما تكون هناك معلومات غير كاملة حول وقت الحدث؛ قد لا يكون الوقت الدقيق معروفًا، ولكن هناك بعض المعلومات المتاحة، مثل حقيقة أن الحدث لم يحدث حتى نقطة معينة (الحذف الأيمن) أو حدث بالفعل قبل بدء المراقبة (الحذف الأيسر). في المقابل، لا يتضمن الحذف أي بيانات على الإطلاق لبعض الأشخاص الذين لا يستوفون معايير الدخول؛ يتم استبعادهم تمامًا من التحليل. تتضمن الأمثلة الأخرى للحذف دراسات حول الأمراض حيث يتم تضمين الأفراد الذين تم تشخيصهم بعد تاريخ محدد فقط، مع استبعاد أولئك الذين تم تشخيصهم في وقت سابق (الحذف الأيسر). وبالمثل، في الدراسات الفلكية، يتم النظر فقط في النجوم القابلة للملاحظة ضمن مسافة معينة، بينما يتم استبعاد النجوم البعيدة جدًا بحيث لا يمكن اكتشافها (الحذف الأيمن).</div>

في تحليل البقاء على قيد الحياة ، يتم قياس الوقت من بداية الدراسة ، مما يضمن مراقبة جميع المشاركين من وقت الصفر حتى وفاتهم أو تعرضهم للرقابة. لكن...

Education

JoVE Core

Statistics

الإحصائيات

Unit 1

الوحدة الأولى

Survival Analysis

تحليل البقاء

KEY TERMS AND CONCEPTS

المصطلحات والمفاهيم الأساسية

left and right truncation in survival data

Truncation in survival analysis describes data loss caused by the timing of an event or by when a subject can enter a study. It can happen in two forms: left truncation and right truncation. In both cases, some individuals are left out of the dataset before analysis begins.

Left truncation happens when people who had the event before a set time are not included in the study. This often occurs with delayed entry, which means a person is only observed if they survive until the entry point. For example, in an occupational study, workers who retired or died before the study started would not appear in the data. That can bias the sample toward people who are still at risk after entry.

Right truncation is less common. It occurs when only individuals who have already had the event by a certain time are included. A mortality study that records only deaths within a specific time window is one example. People who lived beyond that observation period would be excluded.

Truncation is different from censoring. Censoring means the event time is incomplete, but some information is still available. Right censoring tells us the event has not happened by a certain time, and left censoring means it happened before observation began. Truncation gives no data at all for subjects who do not meet the entry rule, so they are completely excluded from the analysis.

Other examples help show the idea. In disease studies, researchers may include only people diagnosed after a certain date, which is left truncation because earlier cases are excluded. In astronomy, right truncation can appear when only stars close enough to be seen are studied, while stars that are too far away are left out.

Left and Right Truncation in Survival Data

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truncation in survival analysis

Truncation in survival analysis describes data loss caused by the timing of an event or by when a subject can enter a study. It can happen in two forms: left truncation and right truncation. In both cases, some individuals are left out of the dataset before analysis begins. Left truncation happens when people who had the event before a set time are not included in the study. This often occurs with delayed entry, which means a person is only observed if they survive until the entry point. For...

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key terms and concepts

Learn how left truncation and right truncation affect survival data, why delayed entry matters, and how truncation differs from censoring.

Left and Right Truncation in Survival Data | JoVE K12

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JoVE Core Statistics introduces the concepts and application of the collection, analysis, presentation, and interpretation of data to students. These animated lessons provide an understanding of statistics beneficial to students from a wide range of disciplines. Additionally, the scientist-in-action videos demonstrate the application of related concepts in classical and original research experiments performed in today's laboratories worldwide

Left and Right Truncation in Survival Data

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