Treatment Allocation Methods Flashcards
Name 4 treatment allocation methods
Simple randomisation
Block randomisation
minimisation
stratifiied sampling
Advantages of Simple randomisation
preserves allocation concealment by being unpredictable
simple
in large trails groups are a similar size
Disadvantages of simple randomisation
Imbalance in groups can lead to a reduction in power
does nit balance group for prognostic factors
possibility of confounding bias as more chance with people with good/bad prognostic factors ending up in one group
for small trails a higher chance of unequal groups
Advantages of block randomization
reduces in balance in group sizes
prevents bias due to secular trends in prognostic factors of patients
Disadvantages of block randomisation
More complicated than simple randomization
with short block length, it is possible to predict treatment
does not balance prognostic factors
Disadvantages of stratified randomisation
more complex which could lead to errors
only feasible with a small number of strata
Advantages of stratified randomization
balances groups on a small number of prognostic factors
Advantages of minimization randomization
balance can be achieved fir more prognostic factors than by using stratified
Disadvantages of minimization ranodmization
complicated
cannot be done in advance due to allocation depending on patients recruited
tedious without software
why stratified over minimization?
stratified maintains a balance of all combinations of factors, minimization balance between each level of a factor but not a combination
problems with alternate allocation?
allocation as it is predictable, because the person recruiting may be aware of the previous allocation and will know the next allocation, which may affect their willingness to recruit a patient. Allocation Bias (Selection Bias)
