# ISA Key Terms (AQA Biology)

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Accuracy
An accurate measurement is one which is close to the true value
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Anomalous Data
Measurements that fall outside the normal or range of measured values. A large number of readings allows anomalous data to be identified with greater certainty.
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Callibration
When using a measuring instrument. Calibration involves fixing known points and constructing a scale between these fixed points
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A change in one variable that is caused by a change in another variable.
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Confounding variable / Control variable
A variable that affects the outcome of the investigation (that is not the IV). These must be kept constant to make it a fair test (control variable)
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Control experiment
One that is set up to eliminate certain possibilities. It is a well designed investigation, the independent variable is changed and all confounding variables are kept constant.
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Control group
An experiment that is treated exactly the same as the experimental group except the factor that is being investigated has not been changed (or added to the method). This allows them to make a comparison.
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Correlation
Shows that there is a relationship between the two variables, however it may not be a causal relationship.
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Dependent variable
The variable that the value of which is measured for each change in the independent variable
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Double-blind trial
A trial (used in medicine) to see the effects of a new drug/treatment on humans. Neither the patient nor the doctors know if they are being treated with the drug or a placebo so that they can avoid bias and increase validity.
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Errors
Errors cause readings to be different from the true value.
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Evidence
The data or observations that are used to support a given hypothesis or belief.
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Fair test
One in which only the independent variable has been allowed to affect the dependent variable. This can be achieved by keeping all other variables constant /controlled
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Hypothesis
Possible explanation of a problem that can be tested experimentally (experimental hypothesis)
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Independent variable
The variable for which values are changed by the investigator.
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Null hypothesis
A hypothesis that is phrased as there being no difference or no association. This is used when it is difficult to predict what would happen as a result of the investigation.
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Placebo
Dummy pill or injection given to members of a control group in medical trials. This ensures that the data collected from a trial are valid.
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Precision
Related to the smallest scale division on the measuring instrument being used. A set of precise measurements will have very little spread around the mean value.
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Probability
The likelihood of an event occurring. It differs from chance in that it can be expressed mathematically. It can be represented using decimals or fractions.
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Protocol
Once an experimental method has been shown to produce valid and reliable results, it becomes a protocol used by other scientists.
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Random distribution
One that arises as a result of chance. This avoids observed bias and allows statistical tests to be used in an analysis of the results of the investigation.
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Random errors
Occur in an unpredictable way. They may be caused by human error, faulty technique in taking measurements or by faulty equipment.
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Raw data
Instrument readings and other data collected at the time of the investigation. These data may subsequently be processed and used to calculate %’s and standard deviations
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Reliability
Results of an investigation may be considered reliable if they can be repeated. If other scientists get the same results, then the results of the initial investigation are more likely to be reliable. This can also be done by taking repeat measurement
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Systematic errors
Errors that cause readings to spread around some value other than the true value. Systematic errors may occur when using a wrongly calibrated instrument.
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True value
This is the accurate value which would be found if the quantity could be measured without any errors
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Validity
Data is valid if the measurements that have been made are affected by a single independent variable only. They are not valid of the investigation is flawed and confounding variable have been allowed to change or there is observed bias. Conclusions ar
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Zero errors
Caused by instruments that have an incorrect zero. E.g when using a balance, if the scale is not on 0 before anything has been placed on it.
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## Other cards in this set

### Card 2

#### Front

Measurements that fall outside the normal or range of measured values. A large number of readings allows anomalous data to be identified with greater certainty.

Anomalous Data

### Card 3

#### Front

When using a measuring instrument. Calibration involves fixing known points and constructing a scale between these fixed points

### Card 4

#### Front

A change in one variable that is caused by a change in another variable.

### Card 5

#### Front

A variable that affects the outcome of the investigation (that is not the IV). These must be kept constant to make it a fair test (control variable)