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Printable Handouts
Navigable Slide Index
- Introduction
- Acknowledgements
- Unequal allocation in clinical trials
- Equal allocation procedures
- Allocation ratio preserving procedures
- Variations in unconditional allocations ratio
- Many unequal procedures lack ARP property
- Variation problems in unconditional allocation ratio
- Randomization test problems caused by variations
- ARP expansions by mapping from equal allocation
- ARP unequal allocation procedures from mapping
- Visualizing randomization sequence
- PBR space can be too wide for unequal allocation
- Brick tunnel randomization
- Allocation space reduction with BTR vs. PBR
- Derivation of transition probabilities for BTR
- Selection bias potential with BTR
- Widening the allocation space
- Limiting imbalance in treatment assignments
- Equal allocation procedures that limit imbalance
- Building wide brick tunnel - the switch technique
- Illustration of the switch technique
- Building WBTR by adding layers of new nodes
- Building WBTR with varying allocation probabilities
- Deriving probabilities of treatment allocation
- Expanding BTR allocation space
- Unequal allocations with narrow allocation space
- Biased coin randomization (BCR) for 1:1 allocation
- BCR for equal allocation to K > 2 arms
- Equal split of bias problem in the preferred arms
- Improved assignment probabilities
- Expanding BCR to unequal allocation
- Unequal allocation BCR with varying probabilities
- Expanding dynamic allocation procedures
- Conclusions
- Thank you
- References (1)
- References (2)
- References (3)
- References (4)
- References (5)
Topics Covered
- Unequal allocation in clinical trials
- Allocation ratio preserving procedures
- Variations in unconditional allocation ratio
- Permuted block design (PBR)
- Brick tunnel randomization (BTR)
- Wide brick tunnel randomization (WBTR)
- Biased coin randomization (BCR)
Links
Series:
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Talk Citation
Kuznetsova, O.M. (2016, September 29). Randomization in studies with unequal allocation [Video file]. In The Biomedical & Life Sciences Collection, Henry Stewart Talks. Retrieved October 11, 2024, from https://doi.org/10.69645/QZNE2796.Export Citation (RIS)
Publication History
Financial Disclosures
- Dr. Kuznetsova has no commercial/financial relationships to disclose
Other Talks in the Series: The Risk of Bias in Randomized Clinical Trials
Transcript
Please wait while the transcript is being prepared...
0:00
Hi. I'm Olga Kuznetsova.
I'm a Senior Principal Scientist
at Merck & Company.
I will talk about
randomization in studies
with unequal allocation.
0:13
This presentation is largely
based on our joint works
with Dr. Yevgen Tymofyeyev.
0:20
Unequal allocation
where the treatment groups
are planned to have unequal sizes
is often used in clinical trials.
Among common reason
unequal allocation
are power considerations,
better enrollment in a trail
with higher allocation
to the experimental group.
Increased exposure
to the experimental treatment
or reduced cost.
Unequal allocation is often used
in adaptive design studies list
two or more treatment times.
Dose-ranging
or multi-stage studies,
studies with treatment
selection design,
sample size re-estimation
or response adaptive randomization.
0:59
Numerous equal allocation procedures
are developed to meet
different design needs.
Robustness with respect
to the accidental bias
due to a time trend,
reduced potential
for selection bias,
balance in important covariates.
This algorithms
are usually symmetric
with respect to the treatment arms.
As a result all patients,
regardless of their place
in the allocation sequence,
are allocated with the same
unconditional allocation ratio.
For example,
in a study with equal allocation
to two treatments,
the patients allocated first,
second, third and so on,
all have probability of ½
to be allocated
to the first treatment.