Planning a fieldwork investigation Cambridge IGCSE Environmental Management revision
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In plain words
Counting every daisy in a field would take a week, so nobody does. They count a sample and work from that. Whether the answer can be trusted depends on how the investigation was planned, and the planning is what the exam tests.
9 things to know
- An aim says what the investigation is trying to find out. A hypothesis is a statement that can be tested, such as "there are more plant species in the unmown area".
- The independent variable is the one that is changed or chosen. The dependent variable is the one that is measured. Control variables are kept the same, so that the test is fair.
- Methods are planned in advance: the sampling strategy, the sampling technique, and any questionnaires or surveys. A pilot study is a small trial run that shows up problems before the real work begins.
- Repeats and replicates: taking the same measurement several times, or at several sites, and using the mean makes the data more reliable.
- Data are recorded in a table with headings and units, and then analysed with calculations and graphs.
- An anomaly is a result that does not fit the pattern. It should be identified, then checked or repeated, and left out of the mean if it was a mistake.
- A conclusion says what the data show, and whether they support the hypothesis.
- Random sampling: sample points are chosen by chance, for example with random numbers used as coordinates on a grid. It avoids bias. It may miss parts of the area by chance.
- Systematic sampling: samples are taken at regular intervals, for example every 2 m along a line. It covers the area evenly and shows how things change across it. It may miss whatever lies between the points.
Worked example
A student wants to find out whether trampling affects the number of plant species on a path and beside it. Identify the variables and suggest a sampling strategy.
- Independent variable: the place, on the path or beside it.
- Dependent variable: the number of plant species counted in each sample.
- Control variables: the size of the sample area, the time of year and the method of counting.
- Strategy: random sampling within each area, with at least ten samples in each, so that the choice of spots is not biased.
Tips and tricks
- Independent: the one I change. Dependent: the one that depends on it, which is what you measure.
- To make results reliable, the answer is repeats and a mean. To make a test fair, the answer is control variables. They are different questions.
It lands in your notebook with its questions as flashcards.
Planning a fieldwork investigation: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is a hypothesis?
The investigation tests whether it is supported.
Which variable is measured?
It depends on what was changed.
Why are measurements repeated?
A mean of several readings is more trustworthy than one.
What is the main benefit of random sampling?
Nobody chooses where the samples go.
A sample is taken every 5 m along a tape. Which strategy is this?
Regular intervals make it systematic.
Why is systematic sampling better than random sampling for studying how plants change from a pond's edge to dry ground?Stretch
A gradual change needs samples all the way along it.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 7 marks. Write your answers on paper, then check them.
Planning a fieldwork investigation
Cambridge IGCSE Environmental Management 0680 · 7 marks · papermunch.org
Name ______________________________ Date ______________
Explain the difference between random sampling and systematic sampling.[2]
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In random sampling, the sample points are chosen by chance. In systematic sampling, samples are taken at regular intervals.
Explain why a pilot study is carried out.[2]
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It is a small trial of the method. It shows up problems, so the method can be improved before the main investigation.
Describe what should be done when one result is very different from the others.[3]
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Identify it as an anomaly. Repeat the measurement to check it. If it was a mistake, leave it out when calculating the mean.
Answers: Planning a fieldwork investigation
- 1. In random sampling, the sample points are chosen by chance. In systematic sampling, samples are taken at regular intervals.
- 2. It is a small trial of the method. It shows up problems, so the method can be improved before the main investigation.
- 3. Identify it as an anomaly. Repeat the measurement to check it. If it was a mistake, leave it out when calculating the mean.