Do I understand about fair testing?

Select the correct answer.

Question 1

A 'fair test' must always involve:

1. only one thing that is changed
2. some way that measurements are made to determine the results
3. the use of specialised science equipment
4. all variables being kept the same

Feedback:

1. That is correct, only the experimental variable is changed.
2. Incorrect. While many 'fair tests' involve measurement, there may be others that could be determined by observations e.g which plant was tallest, which group of people ran fastest. Generally measurement increases accuracy and allows us to calcuate averages, but it is not essential for a 'fair test'.
3. Wrong. Simple equipment and observations can be used to obtain valid results in a 'fair test', so long as it has been carefully planned.
4. No. There must be one difference between the experiment and the control in an investigation for it to be fair.

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Question 2

In the mnemonic Cows Moos Softly:

1. the C in cows reminds us that everything has to be changed
2. the M in moos stands for the variable that is measured
3. the S in softly reminds us to repeat the investigation several times
4. has nothing to do with fair testing

Feedback:

1. Wrong. The C in cows reminds us that only one thing is changed. This is called the experimental or independent variable.
2. Correct! The measured variable is sometimes called the dependent variable. It is what we measure or observe to determine the result.
3. Incorrect. The S in softly reminds us to keep all variables other than the experimental one, the same. We say we control the variables.
4. Wrong. This mnemonic is most useful to help students remember the different types of variables and how they are controlled to ensure a fair test.

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Question 3

Scientists call a general proposition that tries to explain a phenomenon:

1. a prediction
2. an hypothesis
3. a guess
4. a conclusion

Feedback:

1. Wrong. A prediction is what we expect to happen or our anticipated result. It is closely related to the testable question.
2. Correct. Well done! It is useful to understand the meaning of this term but the syllabus does not demand that the students can use it even though many do like to use it.
3. Wrong. To some extent an hypothesis is an informed guess, but scientists use the term hypothesis as a more precise term.
4. A conclusion is a statement that addresses the aim of an investigation and is derived directly from the results.

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Question 4

Repeating an experiment a number of times ensures that it is accurate.

1. True
2. False

Feedback:

1. Incorrect. If the measuring equipment is faulty or the operator not sufficiently skilled, repeating the results will still not make them accurate.
2. Correct. Repeating an experiment ensures reliable results provided the results are all similar, but if the experimental design is not valid, or the measuring process incorrect the results will not be accurate and a conclusion should not be drawn.

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Question 5

When conducting investigations with living things it is often necessary to:

1. replicate the activity
2. ignore results of those that do not survive

Feedback:

1. Correct. Because there is variation in natural populations, it is often necessary to use a number of living things in the investigation to reduce the impact of chance variations and so get reliable results. We often repeat experiments that are non-destructive to get more reliable results.
2. Wrong! You cannot just choose to ignore some of the results as this no longer makes the investigation fair.

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