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Introduction
Introduction
Resource- The unit that follows presents two
sections from different parts of the Maths for Science teaching text – a
course designed to help OU students acquire the knowledge and skills to
tackle the mathematical...
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1 Measurement in science
1.1 Large quantities and small
quantities Resource- Scientists frequently deal with
enormous quantities – and with tiny ones. For example it is estimated
that the Earth came into being about four and a half thousand million
years ago. It took another six...
1.2 Units of measurement Resource- In the UK, two systems of units
are in common use. We still use old imperial measures for some things:
milk is sold in pints and signposts indicate distances in miles. But for
many other everyday measurements...
1.3 Scales of measurement Resource- In thinking about the sizes of
things, it is sometimes useful to do so in quite rough terms, just to
the nearest power of ten. For example, 200 is nearer to 100 than it is
to 1000, but 850 is nearer to...
1.4 How precise are the
measurements? Resource- Scientists are always trying to
get better and more reliable data. One way of getting a more precise
measurement might be to switch to an instrument with a more finely
divided scale. Figure 4 shows parts...
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2 Probability and descriptive statistics
Preamble
Resource- Statistical information is a
familiar aspect of modern life, which features routinely in, for
example, news reports, sports commentaries and advertising. Scientists
who have collected large amounts of...
2.1 Chance and probability Resource- ‘Probability is expectation
founded upon partial knowledge. A perfect acquaintance with all the
circumstances affecting the occurrence of an event would change
expectation into certainty, and leave neither...
2.1.1 Calculating probability Resource- If a process is repeated in
identical fashion a very large number of times, the probability of a
given outcome is defined as the fraction of the results corresponding to
that particular outcome.
2.1.2 Probability and common sense Resource- The concept of probability is a
purely theoretical one. Strictly speaking, no experiment measures a
probability: all that we can measure is the fraction of times a
particular outcome occurs in a finite...
2.1.3 Expressing probability Resource- According to Equation 1,
probability is defined as a fraction. However a fraction such as may
also be expressed as a decimal number or as a percentage:
2.1.4 Combining probabilities Resource- The probabilities described in
Sections 2.1.1 and 2.1.2 related to the outcomes of a single process,
such as repeatedly tossing one coin. Now suppose you were to toss three
separate coins simultaneously....
2.1.5 Probability ratios Resource- Probability calculations are
important in many branches of science, but nowhere more so than in
genetics. Box 4 describes early work in the field and provides some
illustrative data, based on plant-breeding...
2.2 Descriptive statistics Resource- Scientists collect many different
types of information, but sets of data may be very loosely classified
into two different types. In the first type, so-called ‘repeated
measurement’, an individual quantity...
2.2.1 Repeated measurements Resource- Scientists are always concerned
with the reliability and precision of their data, and this is the prime
reason for them to repeat measurements many times. Consider the
photograph shown in Figure 6, which...
2.2.2 The distribution of repeated
measurements Resource- As noted in the previous section,
if the same quantity is measured repeatedly, the results will generally
be scattered across a range of values. This is perhaps best illustrated
using a real example. Table...
2.2.3 Mean and standard deviation
for repeated measurements Resource- In everyday terms, everybody is
familiar with the word ‘average’, but in science and statistics there
are actually several different kinds of average used for different
purposes. In the kind of situation...
2.2.4 Using a calculator for
statistical calculations Resource- Table 3 shows all the values for
each step in the process of calculating a standard deviation, so that
you can see what the operations encapsulated by Equation 7 actually
entail, but you will probably...
2.2.5 How likely are particular
results? Resource- In real experiments, as opposed to
hypothetical ones, it is very rare that scientists make a sufficiently
large number of measurements to obtain a smooth continuous distribution
like that shown in Figure...
2.2.6 Different types of ‘average’ Resource- Figure 8 showed that if the data
have a normal distribution the mean value corresponds to the peak of the
distribution. Normal distributions of data are very common in science,
but by no means universal....
2.2.7 Samples and populations Resource- It is no accident that the
examples used in Sections 2.2.3 and 2.2.4 to illustrate the statistics
for repeated measurements of individual quantities were drawn from
chemistry and physics. Experiments involving...
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References and Acknowledgements
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