Download - RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010
![Page 1: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/1.jpg)
RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS
Dipesh Mistry & Jessica SmithSeptember 2010
![Page 2: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/2.jpg)
OVERVIEWOVERVIEW
• Randomisation-What, why, how and when
• Allocation Concealment
• Bias
• Blinding
![Page 3: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/3.jpg)
WHAT IS RANDOMISATION?WHAT IS RANDOMISATION?
DEFINITIONRandomisation is a process by which each participant has
the same chance of being randomly assigned to one of two or more groups e.g. Group A & Group B.
![Page 4: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/4.jpg)
WHY RANDOMISE?WHY RANDOMISE?
Possible explanations for a difference would include: 1.the intervention exhibits a real effect;
2.the outcome difference is solely due to chance3.there is a systematic difference (bias) between the groups due to factors other than the intervention
Eligible patients
Group A
Group B
Allocate Patients
Analysis
Follow up
![Page 5: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/5.jpg)
WHAT IS ALLOCATION BIAS?WHAT IS ALLOCATION BIAS?
LBPPatients
Less SeverePatients
More SeverePatients
![Page 6: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/6.jpg)
WHAT IS ALLOCATION BIAS?WHAT IS ALLOCATION BIAS?
Is there a difference because:
- the treatment actually works- of the way he has allocated patients
![Page 7: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/7.jpg)
RANDOMISATION DEPENDS ON:
1.the generation of an unpredictable allocation sequence
2. the concealment of that sequence
![Page 8: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/8.jpg)
ALLOCATION RATIO’SALLOCATION RATIO’S1. Equal Allocation
Participants have the same chance of being assigned to trial arms
• Easily accommodates multiple arm studies• Generally the most efficient design• Easy to implement
2. Unequal Allocation• Assigns more participants to intervention• e.g. BEST – 2:1 allocation
![Page 9: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/9.jpg)
TYPES OF RANDOMISATIONTYPES OF RANDOMISATION
• Simple Randomisation
• Permuted Block Randomisation
• Stratified Block Randomisation
• Minimisation Method
![Page 10: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/10.jpg)
SIMPLE RANDOMISATIONSIMPLE RANDOMISATIONDefinitionMost basic form of randomisation where each treatment
assignment is ”memory less” - made without regard to previous assignments
Some examples:• Unbiased coin toss for each trial participant• Roll an unbiased die• Sequence of Random Numbers from statistical textbooks• Computer generated random sequence
![Page 11: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/11.jpg)
ILLUSTRATIONILLUSTRATION
• Two Groups (criteria: {2,4,6,8,0}=A, {1,3,5,7,9}=B):
A computer generated random sequence:
4,8,3,2,7,2,6,6,3,4,2,1,6,2,0,…….
4 8 3 2 7 2 6 6 3 4 2 1 6 2 0A A B A B A A A B A A B A A B
![Page 12: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/12.jpg)
ILLUSTRATIONILLUSTRATIONA computer generated random sequence:
4,8,3,2,7,2,6,6,3,4,2,1,6,2,0,…….
Two Groups: different randomisation ratios (e.g. 1:2)(criteria:{1,2,3}=A, {4,5,6,7,8,9}=B; ignore 0’s)
4 8 3 2 7 2 6 6 3 4 2 1 6 2 0B B A A B A B B A B A A B A -
![Page 13: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/13.jpg)
ILLUSTRATIONILLUSTRATIONA computer generated random sequence:
4,8,3,2,7,2,6,6,3,4,2,1,6,2,0,…….
Three Groups: (criteria:{1,2,3}=A, {4,5,6}=B, {7,8,9}=C; ignore 0’s)
4 8 3 2 7 2 6 6 3 4 2 1 6 2 0B C A A C A B B A B A A B A -
![Page 14: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/14.jpg)
SIMPLE RANDOMISATION SIMPLE RANDOMISATION SUMMARYSUMMARY
Pros and Cons+ Simplistic implementation+ Allocation is random and unpredictable− Can produce unbalanced allocation− Can lead to analysis complications e.g. interim
analyses
Imbalance SolutionReplace with another allocation list (criteria: >10)Restrict the randomisation
![Page 15: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/15.jpg)
BLOCK/PERMUTED BLOCK BLOCK/PERMUTED BLOCK RANDOMISATIONRANDOMISATION
Definition• Allocation list is comprised of “blocks”• Each block contains one possible combination
(permutation) of possible treatment allocations• Allocation is balanced at end of each block
![Page 16: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/16.jpg)
Basic Implementation
1 Block size is an multiple of treatment arms i.e.2 arms → b = {2, 4, 6, . . .}, 3 arms → b = {3, 6, 9, . . .}
2 List all possible combinations e.g.For block size of 2: AB or BA
3 Choose a criteria for each block of patientsDigits 0-4 = AB Digits 5-9 = BA
4 8 3 2 7 2 6 6 3 4 2 1 6 2 0AB BA AB AB BA AB BA BA AB AB AB AB BA AB AB
4,8,3,2,7,2,6,6,3,4,2,1,6,2,0,…….
![Page 17: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/17.jpg)
ILLUSTRATION
1 Lets say: - want to compare 2 groups e.g. Grp A & Grp B- choose block size of 4 patients
2 List allocation combinations for block size of 4AABB BAAB ABBA ABAB BABA BBAA
3 Choose criteria for each block of patients1 - AABB 2 - BAAB 3 - ABBA4 - ABAB 5 - BABA 6 – BBAA ignore 0,7,8,9
4 8 3 2 7 2 6 6 …- -
4,8,3,2,7,2,6,6,3,4,2,1,6,2,0,…….
ABAB ABBA BAAB BAAB BBAA BBAA …
![Page 18: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/18.jpg)
BLOCK RANDOMISATION SUMMARYBLOCK RANDOMISATION SUMMARY
Pros and Cons+ Balance between arms is guaranteed by block’s end+ Interim analysis can still have balance− Bias can occur if allocation sequence is determined
RecommendationsDo NOT use block size of 2Use reasonably large blocks to avoid predictabilityNot too large if interim analysis intended
![Page 19: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/19.jpg)
STRATIFIED BLOCK RANDOMISATION
Definition
Balancing treatment groups with respect to prognostic factors which may be related with participant response in order to prospectively achieve treatment group comparability
![Page 20: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/20.jpg)
WHAT DOES THIS MEAN?WHAT DOES THIS MEAN?
REMEMBER: randomisation is to ensure treatment group comparability
HOWEVER: certain prognostic factors may be predictors of response e.g. age, sex,
THEREFORE: we want to make certain that there is a balance in both groups for these factors
HOW? – have a separate block randomisation scheme for each category
![Page 21: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/21.jpg)
ILLUSTRATIONILLUSTRATION
• Single Strata: Age, (block size 4)
AGE <50 BABA AABB ABBA BBAA BAAB …AGE ≥50 BAAB ABBA BBAA ABAB BABA …
GROUP A GROUP B
AGE <50 50% 50%
AGE ≥50 50% 50%
![Page 22: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/22.jpg)
ILLUSTRATIONILLUSTRATION• Two Strata: Gender & Age, (block size 4)
Male AGE <50 BABA AABB ABBA BBAA BAAB …Male AGE ≥50 BABA AABB ABBA BBAA BAAB …
Female AGE <50 BAAB ABBA BBAA ABAB BABA …
Female AGE ≥50 BAAB ABBA BBAA ABAB BABA …
GROUP A GROUP BMale AGE <50 50% 50%Male AGE ≥50 50% 50%
Female AGE <50 50% 50%Female AGE ≥50 50% 50%
![Page 23: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/23.jpg)
STRATIFIED STRATIFIED RANDOMISATION SUMMARYRANDOMISATION SUMMARY
• Pros and Cons
• + Balance important variables between arms• + Improves power by reducing variance• − Complicates allocation process• − Too many strata can lead to sparse data
![Page 24: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/24.jpg)
MINIMISATION METHODMINIMISATION METHOD
DefinitionMinimisation (Adaptive randomisation) is an accepted
statistical method to limit imbalance in randomised clinical trials in conditions with known important prognostic factors.
Its called minimisation because imbalance in the prognostic factors is minimised
![Page 25: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/25.jpg)
ILLUSTRATIONILLUSTRATION- - Lets say we have 40 patients alreadyLets say we have 40 patients already- Each factor (gender & age) should consist of 40 patients- Each factor (gender & age) should consist of 40 patients- - Next patient (41Next patient (41stst patient) is Female and <50. patient) is Female and <50.
- For each treatment, add number of patients in the - For each treatment, add number of patients in the corresponding 2 rows:corresponding 2 rows:
Group A = 9 + 8 = 17 Group B = 8 + 7 = 15Group A = 9 + 8 = 17 Group B = 8 + 7 = 15
Factor Level GROUP A GROUP B Gender Male 11 12 Female 9 8Age AGE <50 8 7 AGE ≥50 12 13
NEXT ASSIGNMENT TO GROUP B
![Page 26: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/26.jpg)
MINIMISATION METHOD SUMMARYMINIMISATION METHOD SUMMARY
Pros and Cons+ Cannot determine next allocation+ Maintains balance across groups+ Advantage over stratified block randomisation, as
randomisation does not occur within strata− Can be technically challenging to implement
![Page 27: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/27.jpg)
ALLOCATION CONCEALMENTALLOCATION CONCEALMENT- different to blinding- different to blinding- avoids selection bias- avoids selection bias
Trial Type MechanismSingle-centre trial -Independent person responsible for patients
registration and randomization- Use randomisation list or sealed envelopes
Multi-centre Trial After gaining consent from eligible patient:-Central randomisation by telephone-Interactive voice response system-Fax or internet
Central registration office not feasible/desirable
-Sealed envelopes containing treatment allocation inside
![Page 28: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/28.jpg)
PRACTICAL CONSIDERATIONSPRACTICAL CONSIDERATIONS
STUDY TYPE RANDOMISATIONSmall studies BlockLarge studies BlockLarge, Multi-centre studies Stratified Block / MinimisationLarge, prognostics factors Minimisation
![Page 29: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/29.jpg)
RECAPRECAP• Randomisation
- Reduces allocation bias- Ensures comparability of Groups
• Allocation Concealment- Reduces selection bias- Again, ensures comparability of Groups
• OTHER FORMS OF BIAS AFTER RANDOMISATION….
![Page 30: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/30.jpg)
TYPES OF BIASTYPES OF BIAS
• Patient bias
• Care Provider bias
• Assessor bias
• Analysis and Interpretation bias
![Page 31: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/31.jpg)
PATIENT BIASPATIENT BIAS
DEFINITIONThe patients knowledge of the treatment being
received may affect the outcome of the study.
• patient’s knowledge that they are receiving a “new” treatment may substantially affect the patient’s subjective assessment.
![Page 32: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/32.jpg)
CARE PROVIDER BIASCARE PROVIDER BIAS
DEFINITIONThe care provider’s knowledge of which treatment a
patient is receiving may affect the way the provider• Deals with the patient• Treats the patient• May give patient information about the treatment the
patient is receiving
![Page 33: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/33.jpg)
ASSESSOR BIASASSESSOR BIAS
DEFINITIONAssessor’s knowledge of which treatment the patient is
receiving may affect the way the assessor assesses outcome
• Affect validity of conclusion of the study• If assessment conducted whilst patient still receiving
treatment may indirectly provide patient with information about the treatment they are receiving.
![Page 34: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/34.jpg)
ANALYSIS AND INTERPERTATION BIASANALYSIS AND INTERPERTATION BIAS
Knowledge of the treatment arm may affect resultant analysis of the data as
• Seeking explanation of an “anomalous” finding when one is found contrary to the study hypothesis.
• Accept a “positive” finding without fully exploring the data
Knowledge of the treatment arm may affect decisions made by external monitors
• Terminate the study due to adverse events• Terminate the study for superiority of treatment
![Page 35: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/35.jpg)
BLINDINGBLINDINGBlinding = masking treatmentAll of these potential biases can be avoided if everyone
involved within a study is blinded to the treatment being given to the patient.
HIERARCHY OF BLINDING• Un-blinded • Single Blind• Double Blind• Complete Blind
![Page 36: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/36.jpg)
SINGLE BLINDSINGLE BLIND
The patient (or sometimes the clinician) is blinded to the treatment given.
Often used when double blinding is impractical for reason such as
• Need to adjust medication• Potential side effects
![Page 37: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/37.jpg)
DOUBLE BLINDDOUBLE BLIND
Neither the participant nor the physician conducting the study know which treatment is being given to the participant
Minimises both potential patient biases and potential assessor biases
Should be used whenever possible
![Page 38: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/38.jpg)
DOUBLE BLINDING TECHNIQUESDOUBLE BLINDING TECHNIQUES
Placebo for each possible treatment• Tablets identical in physical appearance• Tablets with similar taste and smell• Same carrier used for IV infusions
Other treatments “shammed” as far as possible• Sham surgery
![Page 39: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/39.jpg)
DOUBLE BLINDING- ALWAYS FEASIBLE?DOUBLE BLINDING- ALWAYS FEASIBLE?
Double blinding may not be possible:
• May not be ethically permissible to blind patient
• Study using an exercise intervention
![Page 40: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/40.jpg)
PROBLEMSPROBLEMS WITH WITH DOUBLEDOUBLE BLINDING BLINDING
SIDE EFFECTSIf drug produces side effects = difficult to blind patient and
ethically wrong to produce a placebo that induces side effects.
EFFICACYIf treatment truly effective may become clear as to which
treatment the patient is receiving – rare!
![Page 41: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/41.jpg)
COMPLETE BLINDINGCOMPLETE BLINDING
Effectively it is the best approach BUT
• Requires two groups of people for data processing, one group to encode data and one group to perform the analysis.
• Therefore not economically feasible. Used sometimes by major drug companies
![Page 42: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/42.jpg)
COMPLETE BLINDING COMPLETE BLINDING TECHNIQUESTECHNIQUES
• Analysis uses coded treatment groups
• Analysis uses coded side effects
• Analysis uses coded laboratory tests
![Page 43: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/43.jpg)
SUMMARYSUMMARY• BIAS different types of bias exist in all clinical trials• Randomisation deals with • Allocation concealment deals with • Blinding deals with other types of bias
Allocation bias
Selection bias
![Page 44: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/44.jpg)
THANK YOU FOR LISTENING
ANY QUESTIONS?
![Page 45: RANDOMISATION, BIAS AND BLINDING IN CLINICAL TRIALS Dipesh Mistry & Jessica Smith September 2010](https://reader035.vdocuments.mx/reader035/viewer/2022062422/56649f115503460f94c24852/html5/thumbnails/45.jpg)
Next week…Next week…
BY: Janet Dunn & Louise HillerDATE: Thursday 30th SeptemberTIME: 12.20- 1.45 pm
ROOM: T0.08/09
ANALYSISANALYSISSimple and to the point, defining termsSimple and to the point, defining terms