skills

Question 1

Errors

Answer 1

Mistakes that occur in measurements or calculations. There is an error in every measurement you make because the measuring instrument itself is never exact.
Errors can also occur because:
- an instrument is not working properly
- a person is not using the instrument properly
- a mistake is made reading a scale - parallax error

Question 2

Accuracy

Answer 2

Accuracy refers to how close a measuring result is to the actual result using the best measuring instrumenting available. It is determined by the quality of the measuring device used - more sensitive = more accurate measurements. The finest division used on the scales of an instrument limits the accuracy of the instrument.

Question 3

Reliability

Answer 3

Refers to whether results are repeatable by anyone who tries to do your experiment. If an experiment can be done many times with similar results, the results are said to be reliable.

Question 4

Validity

Answer 4

A valid test refers to whether an experiment tests what it says it is testing. A valid test must have all variables controlled except for the independent variable. A control experiment is necessary to compare with the experiment in which the independent variable is changed. It allows scientists to be sure that any differences in the results have been caused by the variable being tested.

Question 5

Is this method valid?

Answer 5

A method is valid if:

• the measurements are actually measuring what you intend them to measure
• It incorporates suitable equipment, controlled variable and appropriate measuring procedures.

Question 6

Are the results of the experiment reliable?

Answer 6

The results are reliable if:

• the experiment is repeated and the results are the same/similar (within an acceptable margin of error)
• repetition will only determine reliability it will not improve it

Question 7

How could reliability be improved?

Answer 7

Reliability can be improved by carefully controlling all variables (except the experimental variables). The experiment needs to be reproducible.

Question 8

Are these results accurate?

Answer 8

Results are accurate if:

• The design of the experiment is valid
• They are close to the true value of the quantity being measured
• They can be substantiated in secondary sources.

Question 9

How could accuracy have been improved?

Answer 9

By selecting equipment that is appropriate and calibrated for the intended measurements.
- Systematic error is reduced by calibrating equipment

Question 10

Precision

Answer 10

The degree of exactness with which a quantity is measured. It refers to the spread of measurements or results. The precision of a result is limited by the random error in an investigation (fluctuations in measured data due to the precision limitations of the device). Random errors usually result from the experimenter’s inability to take the same measurement in exactly the same way to get exactly the same number. Measurements with large percentage errors represent an inability of getting consistent results and hence make the investigation unreliable.

Question 11

Evaluating a model

Answer 11

Advantages of the model:

• Visualises concept/ makes it tangible
• Simplifies a complex idea for better understanding
• Represents key components/processes
• Allows for predictions
• Helps understanding as major components are represented
• Accurate representation of the process due to choice of material

Disadvantages:

• Can be oversimplified/lack detail
• Not to scale
• Some components not represented/incorrect representation

Question 12

What is the scientific method?

Answer 12

A systematic process of observation, experimentation, measurement and analysis to either support or disprove a hypothesis.