5.0 Practical Skills

Question 1

What does precision mean?

Answer 1

The measurements are consistent and fluctuate about a mean value. (Doesn’t mean the value is accurate).

Question 2

What does Accuracy mean?

Answer 2

A measurement is close to the true value.

Question 3

What does repeatability mean?

Answer 3

The original experimenter can can redo the experiment with the same equipment and method and produce the same results.

Question 4

What does reproducibility mean?

Answer 4

The experiment can be carried out by different people or different techniques/ equipment and the same results are found.

Question 5

What is the resolution?

Answer 5

The smallest change in the quantity being measured that gives a recognisable change in reading

Question 6

What are the types of errors?

Answer 6

Systematic Error
Random Error
Zero Error

Question 7

What is a systematic error?

Answer 7

A consistent and repeatable error due to the equipment, method or technique (E.g. the error has a pattern or trend or bias).

Question 8

What is a random error?

Answer 8

An unpredictable varying of a quantity from one measurement to the next, It can only be reduced by calculating a mean.

Question 9

What is a zero error?

Answer 9

A systematic error due to a non-zero reading when the quantity to be measured is zero. This makes all measured values too high or low.

Question 10

How do you calculate percentage uncertainties when dividing or multiplying?

Answer 10

You add the percentage uncertainties of the values you are multiplying or dividing.

Question 11

How do you calculate the absolute uncertainty when adding or subtracting?

Answer 11

You add the absolutes uncertainties together when adding or subtracting.
For example, if Z=A+B, where A=(4.0±0.1)Ω and B=(1.0±0.2)Ω, then Z=(5.0±0.3)Ω

Question 12

How do you calculate the absolute uncertainty of a mean value?

Answer 12

(Max- Min)/2 = Absolute uncertainty
or
= (Range of data set)/ 2

Question 13

What is the layout of the risk assessment?

Answer 13

Hazard- An object or chemical and the nature of the hazard
Risk - An ‘action’ in the method that can create a risk from a hazard
Control Measure- Must be realistically done in the context of the practical

Example for a resistor
Hazard - Resistor can become hot
Risk - Touching the resistor when in use leading to a burn
Control Measure- Keep hands away from the resistor when in use and leave plenty of time for it to cool.