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Evidence
Definition: something that is issued to support
or develop a Reason and give support for a
Main Conclusion. There are three types of
evidence:
1) Factual assertion ­ a statement that can be challenged and
which is based on information that can be verified e.g. Asda
is better than Tesco because the prices are cheaper
2) Numerical - raw information such as a whole number and
statistical data such as percentages or estimates
3) Personal observations, statements of opinions from a source
­ the quality of this depends on the credibility of the source.…read more

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Issues with numerical and statistical
data
When using research data it is important to think
about the sample that the data was collected from ­
is it large enough/unbiased/representative/reliable?
When an `average' is used it is important to think
about whether this is the mean, median or mode as
these often will each be very different numbers and
anyone can be chosen which best supports their
argument.
Has the evidence been interpreted right?…read more

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Assessing the quality of evidence
Here is what you have to remember when looking at
evidence:
· How large is the sample size?
· How representative is the sample? (in terms of age, gender,
social class, ethnicity etc.)
· What were the circumstances in which the evidence was
collected?
· What is the generalizability (recent and relevant)?
· Is the evidence ambiguous?
· Is it meaningful?
· Is it reliable?
· What alternative interpretations of the evidence is
possible?…read more

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Is this representative?
"95% of Americans think the Texan George Bush is a
wonderful president, according to a recent poll" The
survey was conducted in shopping malls during
Texas during normal working hours.
No because opinions of people in that state may be very different to
those in more Liberal states for example. Also George Bush is Texan so
perhaps the sample were more biased than all Americans in his favour.
The location and time of day appeals to certain groups of people
more, particularly those that are unemployed, and therefore don't
reflect the majority of American adults who do work.…read more

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Generalizability
It's important that the evidence is recent and relevant to the timescale / location /
circumstances /types of people that are being discussed.
Is this recent and relevant?:
"It no longer makes economic sense for families to grow their own
vegetables. The modern day supermarket offers vegetables at a
price that undercuts the cost of growing them for yourself. Marina
Kiblitskaya found that people in Russia spent 25% more money
growing their own vegetables than if they had purchased them in
markets."
No ­ it isn't relevant at all. The evidence used is from Russia and
therefore can not be applied to our country where prices will be
completely different. Also, the data compares the price to markets,
not supermarkets. We also have no idea about what this survey was,
when it was conducted, or who Marina Kiblitskaya is.…read more

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