Why do we Need Randomised Controlled Trials?

1
Why do we Need Randomised Controlled Trials?

• David Torgerson
• Director, York Trials Unit

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What works?

• In most areas, education, health, criminal
  justice, etc, we want to know WHAT or WHETHER
  something works.
• Do bootcamps reduce criminal behaviour?
• Are teaching volunteers effective?
• Are computers effective at improving literacy and
  numeracy?
• Of secondary importance is HOW.

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The WHAT question

• The ONLY way we can find out whether something
  works or not is by using a RANDOMISED CONTROLLED
  TRIAL.
• All other evaluative methods are INFERIOR ways of
  answering the WHAT question and some cannot
  answer it at all (e.g., qualitative research).

4
Structure of Session

• Randomised Controlled Trials ARE the
  gold-standard evaluation method.
• What is wrong with other research methods?
• Why should we do trials

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Before and After Methods
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Clinical Practice in the 18th Century

• "It is incident to physicians, I am afraid,
  beyond all other men, to mistake subsequence for
  consequence."
• Samuel Johnson, 1734

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Background

• Traditionally most interventions have been
  evaluated using a pre-test post-test or before
  and after design.
• Participants are tested treated and then tested
  again any improvements are attributable to the
  intervention.
• Currently this is probably the most POPULAR
  evaluative method in most fields.

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Who uses before and after?

• Policy makers
• Teachers assessing individual children.
• Action researchers.
• Parents
• Lecturers
• We all do.

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Problems

• Problems include
• Temporal changes
• Regression to the mean.

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Temporal Change

• Self-learning irrespective of teaching occurs.
• As children mature they will become better at
  learning.
• Any intervention or treatment is mixed up with
  these temporal changes difficult to disentangle.

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Changes in Outcomes

• If we measured outcome on public examination
  results we will see an improvement. Is this
  because the intervention has worked? Or is it
  because exams have got easier? Or have children
  become more intelligent?
• Without a control group we CANNOT know.

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Regression to the Mean

• As well as temporal changes before and after
  studies are confounded by a statistical
  phenomenon known as Regression to or towards the
  mean

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Regression to the mean

• This is a GROUP phenomenon and occurs when the
  group are measured with an inexact measurement
  tool and then remeasured. Those individuals with
  extreme values will have a high probability of
  regressing towards the mean on the second
  measurement.

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History of RTM

• Galtons work from 1869 started to provide the
  understanding of the phenomenon.
• By 1886 Galton had described the phenomenon among
  the heights of children and their parents
  (children of tall parents tend to be shorter and
  vice versa regression to mediocrity).

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Economists and RTM

• I suspect that the regression fallacy is the
  most common fallacy in the statistical analysis
  of economic data
• Milton Friedman 1992

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Marking Exam Scripts

• For MSc in Health Sciences system of double
  marking markers are blind to student identity and
  the other markers mark.
• There is a tendency to disagree with marks at the
  extreme of the distribution.
• Explanation Regression to mean.

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RTM and exam scripts
18
Annual Increase in offences with firearms
Amnesty
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Did the Amnesty work?

• Unclear, the year preceeding the amnesty had a
  large, unexpected, increase in offences, we would
  expect through regression to the mean that in the
  following year the rate of increase would
  regress back to towards the average annual
  increase.

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Education intervention

• Wheldall selected 40 pupils whose reading was at
  least 2 years behind their peers.
• Half were exposed to an intervention.

Wheldall Educational Review 20005229.
21
Before and after reading programme
Difference highly statistically significant p lt
0.001
22
Before and after reading programme
Differences between groups NOT statistically
significant
23
RTM misunderstanding

• the mean gain scores translated to impressive
  effect sizes of 0.6.
• It could be argued that it is asking too much of
  any program to demonstrate enhanced efficacy on
  top of such high existing efficacy
• control group gains were largely attributable
  to pre-existing literacy programme..
• Perhaps, BUT much of the gain will be due to RTM.

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RTM and School Exclusions

• A qualitative and before and after evaluation of
  an intervention to reduce school exclusions said
• an RCT would not have been able to adequately
  address fundamental problems concerning the
  reliability and validity of quantitative data in
  relation to exclusions

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Flawed Methods

• Selected schools with HIGH exclusion rates on
  which to intervene. Therefore we would EXPECT
  exclusions to fall.
• They did by 15.
• BUT schools with the fewest exclusions INCREASED
  exclusions by 55 whilst schools with the highest
  exclusions had a fall of 32.

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Mentoring

• In England, part of the KS3 Strategy
• Backed by Government and private funding
• Mentoring means a lot of different things
• Research evidence is
• Case studies
• Feelings and perceptions of participants
• Completely inadequate to infer impact

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Neil Applebys Experiment

• A randomised controlled trial involving 20
  underachieving Y8 (12-13 year-old) students
• Matched in pairs on ability and gender
• Randomly allocated in each pair, one mentored,
  the other not
• Mentored group had 20 mins individually every two
  weeks (11 sessions)
• It nearly killed me
• Cost estimated at between 170 and 410 per
  mentored pupil, represents between 8-19 of the
  schools annual per pupil funding for the whole
  of their education

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What the teachers said about the mentored
students

• is a changed person this year she has
  progressed greatly and is a superb helpful
  student.
• Better now, has achieved more, more confident.
• Generally a great improvement recently.
• s attitude and effort have improved over
  the year. He is a lot pleasanter and more willing
  to participate in lessons particularly oral work,
  he responds well to praise.

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What they said about the control group

• Has improved overall this term.
• s attitude and effort have improved over
  the last few months, she is now trying very hard
  to achieve her target. Great effort.
• Commended for attitude and progress.
• has settled since the beginning of the
  year.
• has undergone quite a transformation since
  September. Her attitude towards the teacher and
  her learning have improved drastically and she
  should be congratulated.

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Change in Teachers Ratings of progress, effort
and attitude (English, maths and science
combined)
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What this proves

• If you identify a group of underachieving pupils
  at a particular time and then come back to them
  after a few months, many of them will have
  improved, whatever you did.
• Others (the hard cases) will not have improved,
  whether mentored or left alone.
• The interpretation of this would have been very
  different without a control group

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RTM and League Tables

• RTM GREAT for Governments to help the credulous
  into believing what they do works.
• In any league table those at the bottom will tend
  to regress upwards to the mean whilst those at
  the top regress down. This lends support to
  naming and shaming or extra financial help to
  those at the bottom.

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Dealing with RTM

• The only way to reliably deal with the problem is
  through randomised trials.
• Which is why before and after data are generally
  regarded, by the congnescenti, as almost USELESS.

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History of Controlled Trials

• Because of temporal and regression to mean
  effects we MUST have a control group.

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Background

• Many researchers over the centuries have seen the
  need for a control group to avoid the inherent
  biases in the before and after study.
• Controlled trials have been conducted for several
  hundred years probably occasionally using
  randomisation.

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Scurvy

• Scurvy was a very prevalent condition among
  sailors before the 19th Century.
• A controlled trial in the middle of the 18th
  Century of 12 sailors showed that the two sailors
  allocated to receive lime or orange juice
  recovered and were able to care for their ship
  mates allocated to vinegar or salt water.

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Lack of Dissemination

• An even earlier trial in scurvy prevention used a
  cluster design whereby a whole ships crew were
  allocated citrus fruit and were compared with two
  ships crews who were not.
• The treatment worked but lesson forgotten.
• After second trial took Navy 50 years to
  implement results

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Agriculture

• Fisher is usually thought of as the originator of
  randomisation in the 1920s in agricultural
  experiments.
• He was concerned with the statistical properties
  of randomness as well as the formation of
  unbiased groups.

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Cambridge-Somerfield

• In 1937 a classic experiment the
  Cambridge-Somerfield trial was launched.
• The aim was to show that social worker
  intervention among delinquent boys would reduce
  criminality.

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Design

• 650 boys were identified by their teachers as
  having delinquent behaviour that put them at
  later risk of criminal activity.
• 325 pairs were formed and one from each pair was
  allocated a social worker supported by
  psychiatrists.

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Results early follow-up of boys indulging in
crime.
Green bar indicates intervention grop
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Results later follow-up

• In 1975 boys were followed up again when middle
  aged men.
• 58 of intervention group had NOT had a criminal
  conviction
• BUT 68 of control group had NOT had a
  conviction.
• If a control group had not been used success of
  the intervention would be assured.

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Consequences of the Trial

• The social work profession largely ABANDONED the
  RCT as a method of evaluation as it failed to
  give the RIGHT results.

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RCTs and education

• Lindquist writing about experimental methods in
  1940 argued that advanced text books use all
  illustrations given are in the field of
  agricultural experimentation and are concerned
  with plots blocks yields treatments etc,
  rather than with schools classes scores
  methods pupils etc.

Lindquist Statistical Analysis in Educational
Research, 1940.
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The Importance of Design in Educational
Experiments (Lindquist)

• In 1940 in his book on statistics in educational
  research Lindquist quite clearly describes
  appropriate RCTs for educational research.
• His book is also the first description of the
  appropriate techniques to be used in analysing
  pupils scores in classes (I.e, cluster analysis),
  which was an advance on Fishers Design of
  experiments.

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Cluster analysis

• In health statistics Lindquists statistical
  methods were largely ignored until the late 1980s
  when it became accepted to use the methods he
  advocated to analyse clustered data although even
  now most cluster trials are badly analysed.
• But 64 years on what about his descriptions on
  how to rigorously evaluate educational
  interventions?

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Educational Trials UK

• Not many trials in education have been undertaken
  in the UK.
• Most educational trials are from the USA.
• WHY? (my personal view)
• Futility of the paradigm war
• Failure to understand their importance
• Trials often give the wrong answer
• Lack of funding.

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Opposition to Trials is widespread

• In health care many doctors will refuse to
  believe the results of a trial and argue the
  trial was faulty or poorly conducted if the
  result was wrong.
• Recent example WHI study of hormone replacement
  many doctors REFUSE to accept the findings of
  this study that it INCREASES risk of heart
  disease.

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Opposition to Polio Trial

• I found but one person who rigidly adherred to
  the idea of a placebo control and he is a
  bio-statistician who, if he did not adhere to
  this view, would have had to admit his own
  purposelessness in life (Jonas Salk).

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1950s to 1970s

• The use of trials expanded rapidly within and
  beyond medicine.
• In the social sciences experiments included
• Negative income tax
• Adoption
• Busing
• Public vs private schools
• Prevention of spousal abuse.

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Health Care Trials

• Although ALL new medicines have to be evaluated
  using RCTs many medical treatments do not.
• HOWEVER, health care is fortunate because we
  bury our disasters we KNOW how important trials
  are as a protection for patients.

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Health Care Disasters

• Opposition to RCTs has declined over the years,
  partly due to a number of catastrophes, from
  unevaluated treatments.
• Harmful treatments are still in widespread use
  today we just dont know which ones.

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Disasters among babies

• Routine practice in 40s and 50s to give premature
  infants pure oxygen. At the same time it was
  noted that there was an epidemic of blindness
  among babies. Linked to oxygen use.
• Routine practice in 50s to give prophylactic
  antibiotics to premature infants, caused brain
  damage and death.
• BOTH of these problems only discovered AFTER an
  RCT was undertaken.

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Trial sabotage

• Interestingly an early trial of pure oxygen for
  neonates was sabotaged by nurses who secretly
  gave oxygen to some of the controls because they
  KNEW that it was effective.
• Because of this ARROGANCE they contributed to the
  blinding of healthy babies.

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Educational Disaster?

• On the basis of before and after and anecdote
  widespread implementation of driver education (in
  the USA) among older pupils was implemented.
• It was thought that this would reduce car
  accidents.
• Did it? Fortunately, some sceptics undertook a
  series of trials in the USA.

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Driver Education - Results

• Roberts and colleagues (see Campbell
  Collaboration) reviewed these trials and
  undertook a meta-analysis.
• They found that driver education INCREASED the
  likelihood of deaths in car accidents as it
  increased the prevalence of young motorists.

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UK Policy makers

• Have IGNORED these results and implemented driver
  education in some schools.
• This will directly increase deaths among young
  drivers.

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Computers in Schools

• Introduction of computers into schools has not
  been preceded by large RCTs.
• The best evidence we have is from a
  quasi-experiment from Israel, which showed that
  introduction of computers into half the state
  schools led to no change in Hebrew literacy but a
  DECLINE in maths.
• The Israeli Government has since introduced
  computers into all schools!!!

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Volunteers in Schools

• The use of volunteers to help children learn to
  read is widespread but are they effective?
• In a systematic review of RCTs only 7 trials
  could be identified with largest with ONLY 99
  children.
• The effect of volunteering was very slight (0.19,
  -0.31 to 0.68) and not statistically significant.

Torgerson et al. 2002 Ed Studies, 28 No 4.
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Conclusions

• Virtually all new interventions need to be
  evaluated using RCTs.
• Unlike health care children are compelled to have
  education. Therefore it is even more urgent that
  they should not be exposed to ineffective
  educational interventions.

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We need more trials