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WJEC CBAC

PUPIL GUIDE TO

DOING

CONTROLLED

ASSESSMENTS

IN GCSE SCIENCE

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EXAMS 75%

C O N T R O L L ED A S S E S S M E N T

25%

Controlled assessments make up 25% of your marks for your GCSE.

If you can get a good mark in your controlled assessment, it‟ll be a

great start to getting a good GCSE grade. The worst thing would be

not to hand in a controlled assessment – that would mean it would be

virtually impossible to get a good

GCSE grade.

Controlled assessments are

particularly helpful for people who

get really nervous in their exams.

You do these assessments in class.

If you do really well, it will help you

out if you lose a few marks in the

exams through nerves.

You don‟t have to revise anything to

do well in controlled assessments, but you DO have to know how

scientists work, and, like a scientist, think really carefully about

what you are doing, how you are doing it, and what your results mean.

This booklet takes you through the skills you will need, and gives tips

on how to do really well in your controlled assessments.

The controlled assessment is in three parts:

1. Doing research and using the material to write a report and

design a survey or an investigation.( the RESEARCH AND USE OF

INFORMATION exercise).

2. An experiment, then designing follow-up work (the PRACTICAL

exercise).

Why are controlled assessments important? ?

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3. Watching a DVD of an experiment and doing a risk assessment

and some evaluation of it (the EXPERIMENTAL TECHNIQUES

AND SAFETY exercise).

SYMBOLS USED IN THIS BOOKLET:

Indicates things connected with the RESEARCH AND

USE OF INFORMATION exercise.

Indicates things connected with the PRACTICAL

exercise.

Indicates things connected with the EXPERIMENTAL

TECHNIQUES AND SAFETY exercise.

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The first task of your controlled assessment will always be a

piece of research. Although there is no mark for the research

itself, doing a good job here will make it easier to get a really good

mark on the task that follows. The exam board provides some basic

research material, but for better marks it‟s important that you find

some additional material.

LOOKING FOR SOURCES

On the Internet, start with a search using Google© or another

search engine. Don‟t type too much into the search bar, but do

include enough to make sure you don‟t get loads of useless material.

For example, suppose you want to look for material about genetically

modified crops

Don’t search for:

GM (you‟ll get sites with any word that contains those letters!).

Crops (too vague).

The pros and cons of GM crops (too wordy – will cut out a lot

of relevant sites)

Do search for:

GM crops

Genetically modified crops

Genetic modification

Research skills

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It is worth doing an image search. It can provide you with pictures

and graphs you could use in your report, and can also lead you to

useful articles. It might also be useful to do a video search. You

won‟t be able to use video in your report, but watching a relevant

video may help you understand the topic better

WHAT YOU SHOULD LOOK FOR:

Information backed by evidence.

Experimental data (or data from surveys etc.).

Details of the experiment/survey that produced the data (if

possible).

Relevant pictures, charts and graphs.

You should probably look for at least 5 sources. Sometimes,

sites use material from news agencies, and the information can

be basically the same on a number of different sites. Look for

different sources of information.

ASSESSING THE QUALITY AND BIAS OF DIFFERENT SOURCES

Un-biased sources will usually provide both sides of an argument. If

a source makes out that their point of view is clearly right without

Image search

Video

search

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even mentioning the other side, it is best not to use that site. It‟s

not that biased sources necessarily tell lies, but they can be

„selective‟ about what information they give, missing out relevant

facts that may not fit with their ideas.

You should understand that companies and organisations send press

releases to newspapers and TV companies, who will often put them

into articles without checking all the facts. For this reason, you

should always judge bias by looking at the information, not just the

source. If you can find where the information came from in the first

place, then the source may tell you if the information may be biased.

If the report includes figures, you should try to find out if the data

comes from a well-run scientific experiment.

Good quality experiments will meet the following criteria:

If a sample has been used, it will be big enough (never less than

30, but better to have hundreds or thousands).

Any differences reported should be big enough to be

„significant‟.

You can see that

this report on the

BBC website is

actually from the

UK nuclear

inspectorate. In any

report about

scientific data or

opinion, you should

always try to find

out where the

information actually

came from.

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Make it clear, detailed but

not too long!

The people doing the study should be professional scientists

from a respected organisation.

The experiment/study should have been published in a „peer-

read‟ journal (i.e. someone has looked at the experiment to

make sure it‟s of good quality).

Ideally, other studies should have been done which confirm the

findings – it is always best to be suspicious of reports that find

something completely new or different from other reports.

When you‟ve done your research, you will be asked to write a report

using the information you have collected.

A good quality report will meet the following criteria:

It will focus on the topic or question given and will not include

irrelevant information. This may mean that you don‟t use all the

information you researched.

It will start with an introduction,

stating the purpose of the report.

It will present evidence without bias,

presenting both sides of any argument.

At least some of the evidence will be actual data.

Any explanations will be clear and detailed, but not too

wordy (don‟t “waffle”).

Relevant graphics will be used where they will help to

explain a point.

Writing reports

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Any opinion will be backed up with evidence.

There will be a list of websites, books or any other materials

that you have used in your research.

After doing your research, you will be asked to design some sort of

investigation based on the research topic. This is likely to be a

survey or an investigation using second hand data, not a simple

experiment. You will need to think about the following points:

Will the questions in the survey, or the information collected,

actually answer the question asked or solve the problem?

Will the sample size be big enough? In this sort of exercise, no

sample should ever be under thirty, and sometimes the sample

may need to be a thousand or more. The more variation your

sample is likely to show, the bigger the sample should be.

Is the sample chosen typical of the whole group you wish to

study? For example, if you want to study binge drinking in

males and females under 30, it would be no good if your

samples of males and females all came from large cities,

because lots of people live in smaller towns and villages, so your

conclusions may not be true for the whole country.

Designing investigations and surveys

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In the practical exercise, you will have to design an experiment. This

needs a number of different skills. You may need to:

Identify variables and choose which ones to control for a fair

test.

Design a control experiment.

Choose a range for the variable being tested.

Decide how many repeats will be needed.

Choose a measurement technique that is likely to be accurate.

Make sure that your experiment is „valid‟ (i.e. actually tests the

hypothesis).

Decide how your results will be processed and what you will be

looking for.

EXAMINER TIPS – Research task

Don’t bring in a huge amount of research material – it will take too

long to read through it before you start writing your report (and you

will only have around 45 minutes in total).

The research report should be around 3 sides of writing, including

diagrams and charts. Doing more is unlikely to get you any more

marks, and you could end up doing worse because you rush, or don’t

finish.

What we are looking for is whether you can select relevant

information and graphics, and leave out everything else. A short

report that gets straight to the point and explains the issues clearly will

get the best marks.

You are assessed on your spelling, grammar and presentation – take

care to produce a well laid out, neat piece of work.

Designing experiments

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TYPES OF VARIABLES

Independent variable

What you change – this usually goes on the x axis of any graph.

Dependent variable

What you measure – this usually goes on the y axis of any graph.

Control variable

Any factor (there may be several) which is likely to affect the

outcome of the experiment but which you are not investigating. Not

every variable needs to be controlled – only those that might affect

the experiment. If you‟re not sure if it will affect the experiment or

not, keep it the same.

WAYS OF CONTROLLING VARIABLES

Sometimes this is obvious, but the hints below may help.

Temperature

This is best done with a water bath if the experiment can be put in

water. It is best to use a thermostatically controlled water bath.

pH

This can be controlled with mixtures called buffers. There are

different buffers for different pH values.

Light

If a lamp is being used, the important features are the distance the

lamp is away from the experiment and the wattage of the bulb.

Variables, fair testing and ranges

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Real scientists may

repeat their

experiments 50 or 100

times!

Lamps also give out heat, so a heat shield (a sheet of glass or

perspex or a container of water) should be used.

CHOOSING A RANGE

It is difficult to give general rules, as the choice of range will vary

with the experiment. The range must be neither too big nor too

small. You should choose at least 5 points within the range to take

readings – more if the range is large. The sampling points should be

fairly evenly distributed within the range.

If you are going to have confidence in your results, they ideally need

to show „repeatability‟ (i.e. when repeated, the results are similar).

You cannot possibly tell if the results are repeatable if you don‟t

repeat them a number of times. In school, experiments are often

repeated three times, but that is because of the time available –

„real‟ science experiments would often be repeated many more times.

Some results are more

repeatable than others.

If the readings vary

quite a lot, you can still

have some confidence in

your results if you do a

very large number of

repeats and take an

average.

Repeats and repeatability

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When you design an experiment, you can only guess how many

repeats might be needed. If you have done a similar experiment

before you will have some idea of repeatability. Once you actually

start taking results, you see how repeatable the results are and you

can then decide how many repeats may be needed.

Measuring instruments have different resolutions. The resolution is

to do with the smallest measurement they can read, e.g.

a thermometer may read to the nearest 5oC, 1oC

or 0.5oC. It is always best to use a measuring

instrument with the highest resolution available.

Electronic instruments are not necessarily more

accurate than non-electronic ones. Digital

instruments are not necessarily more accurate than

analogue ones. IT ALL DEPENDS ON THEIR RESOLUTION.

When you design an experiment, you should say how you will process

your results. But, what does “processing” mean?

Processing may include (depending on the experiment):

Choosing measuring instruments

Processing results

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Calculating means.

Calculating percentages.

Calculating rates.

Drawing tables.

Drawing graphs (bar, line or pie).

Your description of the method should be clear and detailed. It is

usually best to present it as numbered steps. You should also include

a list of apparatus.

When you get the results of the experiment set in task A, you will

need to analyse them.

A good quality analysis will include:

A description of any pattern, relationship or trend in the

results.

Identification of any results that don‟t fit the pattern

(„outliers‟) – although these should be picked up during the

experiment and re-done.

Writing your method

Analysing results

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A statement about whether you think the results support the

hypothesis or not (or if they are inconclusive).

A comment about how strong the evidence is.

Evidence is strong when:

Any differences seen are large enough to be „significant‟.

The results are repeatable (i.e. they don‟t show large

variations).

The results are „reproducible‟, i.e. different experimenters get

very similar answers.

The number of repeats is adequate.

EXAMINER TIPS – Practical task

The sheet you are provided with gives you guidance, but not always

complete details of the practical method you should use. If it does not

provide full instructions, think about the best way to do the

experiment.

The practical you do will be similar to the method you should use

when you have to design an experiment for task B. You will simply

have to change some details.

When you describe the method you have designed for task B, make

sure to include as much detail as possible. Don’t just refer to Task A

and say you’ll do it the same way.

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The third exercise in the assessment looks at „experimental

techniques and safety‟. You will have to do a risk assessment of an

experiment that you see on a video clip.

A good risk assessment includes:

A list of all the hazards and why they are hazardous (e.g. acid

is corrosive, iodine is an irritant etc.).

A list of the risks (things that you do in

the experiment) which might result in

danger.

Suitable precautions you could take which

will reduce or prevent the risk.

Sometimes, a hazard may not actually present a

risk in the experiment. For instance, something

may be flammable, but if there is no naked

flame or anything that might cause a spark in

the experiment, there will be no risk.

Some experiments have no hazards and/or no significant risks.

DEFINITIONS

Hazard: A chemical or piece of apparatus that could cause

harm.

Risk: An action involving a hazard that might result in

danger.

Risk assessments

A good risk assessment

prevents anyone doing the

experiment from putting

themselves in danger

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Precaution: Something that can be done to reduce or prevent a

risk, while still allowing you to carry out the

experiment.

You may be asked to evaluate the method used in the experiment

you see, and/or suggest improvements.

A good evaluation will:

Identify any points in the experiment which might have caused

the results to be inaccurate.

Consider how repeatable and (if appropriate) reproducible the

results were. If there were large variations, are there any

changes that might have improved this?

If the results were repeatable and reproducible, and there is no

indication of inaccuracy, then no improvements are necessary. If

not, then changes should be suggested that might improve accuracy,

repeatability and/or reproducibility.

Evaluating experiments

EXAMINER TIPS – Experimental techniques and safety task

Any risks you give must be possible, when someone does the

experiment properly and sensibly.

You need to describe exactly which action in the experiment would

cause a risk, and how.

It’s OK to say there are no risks in an experiment, if that is true.

Even if something is hazardous, it won’t always provide a risk.

Precautions must be practical.

Remember to evaluate the experiment, not the person doing it.