Statistiek 8

Question 1

4 assumptions of Kaplan Meier Survival analysis

Answer 1

• events are unique and oncly occur once
• prognosis for censored patients and survivors is equal
• prognosis for early and late included patients is equal
• events happen at the registred time only

Question 2

Definitie S(t)

Answer 2

Cummulatieve survival probability at time (t)

Question 3

Af te leiden van Kaplan meier curve (2 vragen)

Answer 3

• proportie die nog leeft bij tijdstip t
• point at which 0% has died
• mediane survival time? S(t) = 0.50,

Question 4

Survival probabilty formule:

Answer 4

P (surv time “i” | at risk) = (Ri-Di) / Ri.

i = specifieke dag
Ri = aantal patienten voor dag i
Di = aantal events op moment t

Question 5

Survival op dag 3 berekene hoe?

Answer 5

Het product van de kans dat je dag 1 overleeft, de kans dat je dag twee overleeft.

Question 6

Survival functie: t3

Answer 6

S(t3) = ((R1-D1)/R1) * (R2-D2/R2) * (R3-D3/R3)

stel er gaat nietmand dood op dag 1 en 2 dan is S12 = 1.
Dan 1* (r3-d3)/r3

Question 7

Log rank test?

Answer 7

Non parametrisch, distribution of observed events as expectd under H0 is true (no difference)

If survival group A = survival group B, number of events at any time is proportional to the group size.