EVALUATING EVIDENCE AND DRAWING CONCLUSIONS

Chapter 3 contained exercises in drawing conclusions on the basis of information assumed
to be true. The following examples illustrate some of the circumstances in which one
may attempt to draw conclusions on the basis of consideration of the reliability and the
plausibility of evidence. Example 1 is an imaginary scenario in which the reliability of
the evidence provided by witnesses or participants must be assessed. Someone engaged in
police or legal work, and people who are members of juries at criminal trials, would have
to make these kinds of assessments, and draw conclusions from them. Examples 2 and 3
present extracts from newspaper articles on topical issues. You may often read such articles
and wonder how reliable is the evidence they contain, and what conclusions can be drawn
from it.
Example 1: Matt in the night club
Last Friday night there was an alleged incident in the Jazza club. Matt, a university
student, claims that at about 10.30 pm he was head-butted on the dance floor of
the club, thereby receiving an injury to his nose. A visit to the A and E Department
later that evening confirmed that his nose was broken. He said that because it was
dark, and because he had just turned to walk off the dance floor, he did not get a
clear view of the person who attacked him. Matt’s friend Joe told the management
of the club that a group of four young men left the dance floor immediately after
Matt stepped off, and that one of them was Carl, who had been known to be
involved in attacks on university students, including Joe himself.
A girl who had been talking to Matt and Joe earlier in the evening told the management
that she knew Carl, that he had always been pleasant towards her, and that she
was sure that he wouldn’t do anything violent. She insisted that she was not his
girlfriend, although he had asked her for a date recently, which she didn’t accept
because she was still with her last boyfriend.
Two bouncers at the club were in the room at the time, but said they had seen
nothing of the incident. One of them said, ‘People are always claiming that somebody
has injured them, but it usually turns out that they were drunk and either fell
over or bumped into something.’
Carl was identified from a CCTV video which showed him and his friends leaving
the club at 10.30 pm, apparently laughing and joking. After Matt had reported the
incident to the police, they interviewed Carl and his friends, all of whom denied any
knowledge of such an incident, and claimed never to have noticed Matt at the club.
Let us consider first the plausibility of the allegation. Matt’s claim is plausible, in that a
blow on the nose from someone’s skull could cause a fracture of the bone, and it would
have been possible, in the darkness and confusion, for him to have been unaware who
attacked him. He hasn’t accused any particular person, so his allegation is simply that
someone struck him on the nose, causing a fracture, and this is the kind of thing that could
happen. From the information given, we have no reason to think that Matt was lying, but
he may have been confused as a result of drinking alcohol. However, it is unlikely that he
would have sustained this kind of injury from falling or bumping into something.
What can we conclude from Joe’s evidence? Given his previous experience of Carl, he may
have been more likely to notice him than to notice others who had been close to where
Matt was standing, and who could have attacked him. It is also possible that Joe simply
wanted to get Carl into trouble, and that Carl, though he was certainly in the club, was not
close enough to Matt to have caused the injury.
The girl’s evidence seems to give support to Carl, though she is not an eye witness. She is
not his girlfriend, so her statement cannot be discounted on the grounds that she has a
personal interest in protecting him. On the other hand it is not clear how well she knows
him, and her comments that she turned him down when he asked for a date suggest that
Carl may have had a motive to attack Matt, if he had seen her talking to Matt and Joe.
The bouncers’ evidence is not conclusive. Matt could have been attacked without their
noticing it, and given that it is part of their job to minimise trouble in the club, they would
want to play down the possibility of any such incident.
The fact that Carl and his friends were leaving the club, apparently laughing and joking,
at around the time the incident is said to have occurred proves nothing. Their leaving at
this relatively early time in the evening could have been for reasons other than wanting to
avoid accusations. The denial of involvement by Carl and his friends can be discounted,
because if they had been involved they would not have admitted to it, and in this case
corroboration does not confirm the reliability of their evidence, because either group
loyalty or possibly threats from Carl may influence their statements.
The most that it is reasonable to conclude, without evidence from other witnesses, is that
Matt probably was injured as a result of being head-butted by someone, but there is
insufficient evidence to conclude that Carl, or any one of his friends, is the guilty person.
Example 2: Is homework for school children necessary or desirable?

A new book, The Homework Myth, by American academic Alfie Kohn claims that
homework does not improve children’s performance in tests, causes family conflict and
turns children off education. Kohn, who lectures, carries out research and writes about
education, psychology and parenting, says that children should be able to relax once
they get home from school. In Britain guidelines set by David Blunkett when he was
Education Secretary recommend that four- to five-year-olds should do 20 minutes of
homework per night, rising to 40 minutes at age nine, and to one and a half to two hours
at age sixteen.
The following extracts on the topic of homework come from an article in The Independent
Online Edition of 30 January 2007 by Richard Garner, Education Editor.
‘There is international evidence to suggest Alfie Kohn may have a point on test
scores, if children are set too much homework. The Third International Maths and
Science Survey, published in 1998, found that children who did a moderate amount
of homework did a little better than those who do a lot or very little. For instance,
the Finns, who do less homework than the British, score considerably better in
international tests – coming top of almost every table for maths and science
achievement through the ages of compulsory schooling. The Italians, who do more
homework than the British, do less well.’
‘[David Blunkett’s] argument was: “Surely it is not a lot to ask an 11-year-old who
spends three hours in front of the TV to work for half an hour?” The verdict given in
Homework: The Evidence by Sue Hallam of London University’s Institute of Education
– considered by many people to be the most detailed study of homework – is:
“Studies comparing homework with supervised study have generally found homework
to be superior in increasing attainment but there are exceptions – particularly
at elementary school level. “Maths is the subject children are most likely to improve
in through homework”, she adds.’
‘Mr. Blunkett’s decision to produce the guidelines was based on research which
showed that only 5 per cent of schools in the UK set maths homework three days
a week for nine- to ten-year-olds, compared to more than 80 per cent in other
countries such as France, Hungary, Switzerland and the United States.’
‘Ms Hallam argues that homework needs to be “meaningful”, adding: “Homework, if
taken to the extreme, can completely disrupt family life.” Kohn would go much
further than this – arguing children should engage in things like creating their own
work of art using recycled materials, design a poster with their parents about their
favourite toy and devise a maths quiz to play with other pupils. He would outlaw
exercises such as learning times tables, lists of spellings and completing a set of sums
from a textbook out of school.’
In order to decide what conclusions we can draw from the evidence presented above, we
must first assess the reliability of the evidence itself.
The first authority mentioned is Alfie Kohn, who clearly has some expertise in the field of
education, given that he is an academic who lectures and researches in this area. No doubt
details of his research on the topic of homework are given in his book, and it would be
necessary to read this in order fully to assess the evidence. However, we have no reason to
think that he is presenting anything other than his own considered view.
A second authority, Sue Hallam, also appears to have the appropriate expertise, since
she works in London University’s Institute of Education. The author of the article (the
Education Editor who will be familiar with opinion in this area) reports that her study is
considered to be very detailed.
As Education Secretary, David Blunkett is a politician, and not necessarily an expert on
education. What is described in the extract as his ‘argument’ is not an argument, but a
remark aimed at defending his decision to set guidelines on the amount of time children
should spend doing homework. His decision is said to have been based on research, and we
can assume that the Education Editor of The Independent will have reported this research,
and also the results of the Third International Maths and Science Survey, accurately.
So we have no reason to think that the reports of the various research projects are being
misrepresented here, but we have two experts apparently disagreeing on the topic. There is
some agreement, however, both claiming that homework can disrupt family life, and
both apparently accepting that setting tasks for children to do at home is not bad in itself,
but that the amount of homework, and the kind of task set, determines its usefulness
and desirability. The principal disagreement concerns the effectiveness of homework in
improving the performance of children. Could both experts be right? Given that their
research has been carried out in different countries, it is possible that differences in the
kind of homework children were given and in the kinds of tests or examinations in
relation to which the effectiveness of homework was assessed account for the different
conclusions.
What conclusions can we draw from the results of the Third International Maths and
Science Survey? Without further information, the most we can conclude is that doing a lot
of homework may not help children to do well in international tests. It is possible that
differences other than the amount of homework done in the countries mentioned account
for differences in performance – for example, differences in teaching methods, quality of
teachers, amount of time spent studying maths and science.
The information about the research upon which Mr Blunkett based his guidelines is
insufficient to draw a conclusion about the effectiveness or desirability of homework, since
it simply concerns the amounts of maths homework that children are given in different
countries, and not the results of giving children more maths homework.
So from these extracts we cannot draw firm conclusions about whether homework is
useful or harmful, necessary or unnecessary for high attainment in education. It is often
the case that reading about research on a topic prompts us to ask further questions. In
Chapter 7 more will be said about how to attempt to answer such questions in order to try
to write your own arguments or make decisions on controversial issues.
Example 3: Speed cameras; do they increase road safety?
Consider the following extracts on the topic of speed cameras.
(i) Extracts from: Cameras keep majority of car drivers under the urban limit
‘More than half of car drivers are complying with 30mph speed limits for the first
time, according to official figures, which suggest that speed cameras have altered
drivers’ behaviour.
The proportion of drivers who break the limit in built-up areas fell from 72 per cent
in 1996 to 49 per cent last year.
The improvement in compliance appears to have contributed to a sharp fall in
pedestrian deaths, down by a third in the past decade, from 997 in 1996 to 671
in 2005.
The Department for Transport monitored the speeds of different types of vehicles in
free-flowing conditions on several types of road.
The measurements were taken well away from speed camera sites to ensure that the
results were not distorted by drivers slowing down briefly. The proportion of drivers
in a 30mph area travelling faster than 35 mph, the lowest speed at which cameras
are triggered, has halved from 37 per cent in 1996 to 19 per cent last year.
However, the proportion travelling at more than 10mph above the 70mph limit on
motorways has fallen only slightly over the same period, from 19 per cent to 17 per
cent.’
‘Paul Watters, the AA’s head of roads policy, said that the big increase in speed
camera fines, from 260,000 in 1996 to two million in 2004, had made drivers pay
more attention to the limit. More than a million drivers have six or more penalty
points on their licences and are only one conviction away from an automatic sixmonth
ban, according to a survey last week.
Mr Watters said that satellite navigation systems which inform drivers of the limit
on the road they are on may also have played a part in improving compliance.’
‘The RAC Foundation said that a greater police presence was needed on the roads to
deter a hard core of car drivers and motorcyclists who obeyed the limit only when
they spotted cameras.
Paul Smith, founder of the Safe Speed antispeed camera campaign, said that the fall
in pedestrian deaths was partly the result of a 16 per cent decline in walking.
“It’s not exceeding the speed limit that causes the crash – it’s driving like a nutter,”
he said. “Just because people are driving more slowly on some types of road does not
mean those roads are safer.” ’