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Types of Censoring

Recap

Survival Analysis - Time to the occurance of a given event

Recap & Intro

Exposure

(Cancer)

Event

(DEATH)

time

Censoring??

Censoring

It occurs when we don't even know the exact time-to-event for an included observations.

TYPES OF CENSORING

LEFT INTERVAL RIGHT

Types of Censoring

We know the time- to - event is LESS THAN some value

We know time-to-event is BETWEEN 2 VALUES

We know that the time-to-event is GREATER THAN some value

ti < x

ti > x

x1 < ti < x2

Situation

Examples

An epidemiologist wishes to know the age at diagnosis in a follow-up study of diabetic retinopathy. At the time of the examination, a 50 year old participant was found to have already developed retinopathy , but there is no record of the exact time at which initial evidence is found.

Let's denote x=retinopathy

x found on 50 years :

X

50

Continuation from the situation

If the initial records indicate that at age of 45, the patient in the example above did not have retinopathy.

Continuation

X

45

50

From Study

Situation 2

Estimating Survival time after diagnosis of pancreatic cancer (Wahutu, 2016)

1997

2012

X

O

- The people stay alive at the end of study

- People lost to follow up

3 TYPES OF RIGHT CENSORING

Type I Censoring

RIGHT Censoring

6 months

6 animals

died (uncensored observation)

survive - killed as sacrifice (censored observation)

Type II Censoring

wait until a fixed portion of animals died (80/100 died for example).

Then, the surviving anias are sacrificed.

Type II Censoring

Type III Censoring

- The patients enter the study at diff times during this period.

- some may die beofre the end of the study (exact survival times are known).

- Some may lost / withdraw before the end of the study(Censored Observations).

15 years

REMEMBER THIS !!!

REVISION

1) ti < x = LEFT CENSORING

2) x1 < ti < x2 = INTERVAL CENSORING

3) ti > x = RIGHT CENSORING

TRY THIS OUT !

Inspired by Madison Beer's song 'Reckless'

Exercise

1) Madison Beer found out her boyfriend was cheating. But she doesn't know since when did her boyfriend cheating her. What type of Censoring is this?

Answer : Left Censoring

2) Madison Beer know the girl her boyfriend was cheating on before. They've met before this. But during that time, her boyfriend meeting the girl for the first time. So we can say that the duration when her boyfriend starts cheating on her can be from the moment they know till she found out.

Answer : Interval Censoring

3) After breaking up, her boyfriend (now EX BOYFRIEND) is with that girl. She hope her boyfriend was not happy and eventually break up with that girl too. But we're not sure either they will break up or not as she don't know what happened to them after she broke up with him.

Answer : Right Censoring

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