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Flashcards in Experiment Key Words Deck (37)
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1
Q

Accuracy

A

A measurement result is considered accurate if it is judged to be close to the true value

2
Q

Calibration

A
  • Marking a scale on measuring instrument
  • This involves establishing the relationship between indication of a measuring instrument and standard or reference quantity values, which must be applied e.g. placing a thermometer in melting ice to see wether it reads 0 degrees Celsius, in order to check if it has been calibrated correctly
3
Q

Data

A

Information, either qualitative or quantitative, that have been collected

4
Q

Measurement Error

A

The difference between a measured value and the true value

5
Q

Anomalies

A

These are values in a set of results which are judged not to be part of the variation raised by random uncertainty

6
Q

Random Error

A
  • These cause readings to be spread about the true value, due to results varying in an unpredictable way from one measurement to the next
  • Random errors are present when any measurement is made, and cannot be corrected. The effect of random errors can be reduced y making more measurements and calculating a new mean
7
Q

Systematic Error

A
  • These cause readings to differ from the true value by a consistent amount each time a measurement is made
  • Sources of systematic error can include the environment, methods of observation instruments used
  • Systematic error cannot be dealt with by simple repeats
  • If a systematic error is suspected, the data collection should be repeated using a different technique or a different set of equipment, and the results compared
8
Q

Zero Error

A
  • Any indication that a measuring system gives a false reading when the true value of a measured quantity is zero e.g. the needle on an ammeter failing to return to zero when no current flows
  • A zero error may result tin a systematic uncertainty
9
Q

Evidence

A

Data that has shown to be valid

10
Q

Fair Test

A

A fair test is one in which only the independent variable has been allowed to affect the dependent variable

11
Q

Hypothesis

A

A proposal intended to explain certain facts or observations

12
Q

Interval

A

The quantity between readings e.g. a set of 11 readings equally spaced over a distance of 1 metre would give an interval of 10 centimetres

13
Q

Precision

A
  • Precise measurements are ones in which there is very little spread about the mean value
  • Precision depends only on the extent of random errors-it gives no indication of how close results are to the true value
14
Q

Prediction

A

A predication is a statement suggesting what will happen in the future, based on observation, experience or a hypothesis

15
Q

Range

A
  • The maximum and minimum values of the independent or dependent variables
  • For example a range of distances may be quotes as either; ‘From 10cm to 50 cm’ or ‘From 50cm to 10cm’
16
Q

Repeatable

A

A measurement is repeatable if the original experimenter repeats the investigation using the same method and equipment and obtains the same results

17
Q

Reproducible

A

A measurement is reproducible if the investigation is repeated by another person, or by using different equipment or technique, and the same results are obtained

18
Q

Resolution

A

This is the smallest change in the quantity being measured (input) of a measuring instrument that gives a perceptible change in the reading

19
Q

Sketch graph

A

A line graph, not necessarily on a grid, that shows the general shape of the relationship between two variables. It will not have any points plotted and although the axes should be labelled they may not be scaled

20
Q

True Value

A

This is the value that would be obtained in an ideal measurement

21
Q

Uncertainty

A

The interval within which the true value ca be expected to lie, with a given level of confidence o rporbeility e.g. “the temperature is 20 degrees Celsius plus minus 2 degrees Celsius, at a level of confidence of 95%”

22
Q

Validity

A

Suitability of the investigative procedure to answer the question being asked. For example, an investigation to find out if the rate of a chemical reaction depended upon the concentration of one of the reactants would not be a valid procedure if the temperature of the reactants was not controlled

23
Q

Valid conclusion

A

A conclusion supported by valid data obtained form an appropriate experimental design and based on sound reasoning

24
Q

Variables

A

These are physical, chemical or biological quantities or characteristics

25
Q

Categoric Variables

A

Categoric variables have values that are labels e.g. names of plants or types of material or reading at week 1, reading at week 2 etc.

26
Q

Continuous Variables

A

Continuous variables can have values (called a quantity) that can be given a magnitude either by counting (as in the case of the number of shrimp) or bu measurement (e.g. light intensity, flow rate etc.)

27
Q

Control Variables

A

A control variable is one which may, in addition to the independent variable, affect the outcome of the investigation and therefore has to be kept constant or at least monitored

28
Q

Dependent Variables

A

The dependent variable is the variable of which the value is measured for each and every change in the independent variable

29
Q

Independent Variables

A

The independent variable is the variable for which values are changed or selected by the investigator

30
Q

Nominal Variables

A

A nominal variable is a type of categoric variable where there is no ordering of categories (e.g. red flowers, pink flowers, blue flowers)

31
Q

Random error, what are some reasons?

A

An error that affects a measurement in an unpredictable fashion

  • Observer error (writing down a measurement wrong
  • The readability of the equipment (e.g. trying to measure the height to which a bouncy ball rises, or reading an ammeter when the current is changing quickly
  • External factors in the measured item (e.g. changes in ambient temperature or pressure in gas measurements)
32
Q

What are some reasons for systematic error?

A
  1. Poor technique (e.g. not avoiding parallax when reading an analogue voltmeter)
  2. Zero error on an instrument (e.g. a newton-meter that shows a value for force when there is nothing hanging from it)
  3. Poor calibration of the instrument (the scale on a thermometer being incorrect so that one degree is too large)
  4. The wrong unit being recorded
33
Q

How can a systematic error be reduced?

A

-Will NOT be reduced by repeating measurements
-Use different methods or instruments to obtain the same value will allow you to compare he results obtained and may identify a systematic error
E.G temperature with mercury thermometer, infrared camera, bimetallic strip thermometer would allow a comparison to be made between instruments

34
Q

What is parallax?

A

Occurs when the position of an object appears to be different when viewed from different positions. This can lead to measurement errors. A mirror is often placed behind the pointer of metres so that by lining up the pointer and its image you know you are avoiding parallax

35
Q

How can you take into account systematic errors?

A
  1. Correcting the value of the readings taken
    E.G if a newton meter has a systematic error of +0.2N then we can subtract this from our results to obtain a more accurate value
36
Q

What is the sensitivity of an instrument?

A

A sensitive instrument produces a large change in output for a small change in input E.G a sensitive analogue ammeter is one that shows a large deflection for a small change in current

37
Q

What is the resolution of a measuring instrument?

A

Resolution is the smallest observable change being measured by a measuring instrument
E.G measuring diameter of metal bar that is about 3mm in diameter, could use a ruler that can measure to the nearest 0.5mm or they could use a micrometer such can measure tot he nearest 0.005mm and the micrometer will give a more accurate measurement with greater resolution