# Data and Uncertainties Flashcards Preview

## Physics > Data and Uncertainties > Flashcards

Flashcards in Data and Uncertainties Deck (42)
1
Q

A

The values found from a single judgment when using a piece of equipment

2
Q

Measurements

A

The values taken as the difference between the judgments of two values

3
Q

Assessing uncertainty

A

Resolution of the instrument used

Manufacturer’s tolerance on instruments

Judgements that are made by the experimenter

Size of increments available

4
Q

A

At least plus or minus half of the smallest division

5
Q

Uncertainty of a measurement

A

At least plus or minus one of the smallest divisions

6
Q

Uncertainties in given values

A

E.g. Charge of an electron is given as 1.60x10^-19

Uncertainty is + or - 0.01x10^-19

Assume he uncertainty to be plus or minus 1 in the last significant digit

7
Q

Repeated measurements

A

A method for reducing the uncertainty

Uncertainty in this case = half the range

8
Q

A

9
Q

Error bars in physics

A

Plot data points at their
mean value

Calculate the range of data ignoring any anomalies

Add error bars with lengths equal to half the range

10
Q

Variable and graph axis

A

X axis - independent variable (the variable that caused the observed effect) it isn’t affected by the other variable

Y axis - dependent variable (the variable that was effected by the independent variable)

11
Q

Scientific ideas

A

The scientific community only accepts new ideas when they can be independently validated

This means others are able to reach the same conclusion

12
Q

Uncertainties in using immersion heater experiment to calculate specific heat capacity

A

Temperature varies throughout - stir

Some of the input energy is use to raise the temperature of the heater and the container

Temperature will continue to rise after the heater has been turned off - find max temperature

Uncertainties in ammeter, voltmeter and thermometer

13
Q

Combining uncertainties

A

If you are adding or subracting values you add the absolute uncertainties

If you are dividing or multiplying then you add the percentage uncertainties

If you are raising a number to a power then you multiply the percentage uncertainties by that power

14
Q

A

More accurate data
Higher sampling rate
Data can be displayed in real time

15
Q

Random errors

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 by making more measurements and calculating a new mean.

16
Q

Systematic errors

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 or instruments used.

Systematic errors 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.

17
Q

Zero errors

A

Any indication that a measuring system gives a false reading when the true value of a measured quantity is zero, eg the needle on an ammeter failing to return to zero when no current flows.

A zero error may result in a systematic uncertainty.

18
Q

Anomalies

A

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

19
Q

Precision

A

Precise measurements are consistent, they fluctuate slightly about a mean value - this doesn’t indicate the value is accurate

The closeness of measurements to one another

20
Q

Resolution

A

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

21
Q

Accuracy

A

The level of conformity of a measurement to the actual value

22
Q

How to determine if something is vertical ?

A

Use a plumb line

Use a spirit level

23
Q

Reducing uncertainty

A

Longer time/distance/relevant variable - reduces percentage uncertainty

24
Q

Percentage uncertainty in a y intercept

A

Best intercept - worst intercept/best intercept x 100

25
Q

Measurement error

A

The difference between a measured value and the true value

26
Q

Evidence

Fair test

Hypothesis

Prediction

A

Data that has been shown to be valid

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

A proposal intended to explain certain facts or observations

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

27
Q

Interval

A

e.g. a set of 11 readings equally spaced over 1 m would give an interval of 0.1 m

28
Q

Repeatable

A

An experiment is repeatable if the original experimenter repeats the experiment using the same method and obtains the same results

29
Q

Reproducible

A

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

30
Q

Uncertainty

A

The interval within which the true value can be expected to lie, with a given level of confidence or probability

31
Q

Validity

A

32
Q

Valid conclusion

A

A conclusion supported by valid data, obtained from an appropriate experimental design and base on sound reasoning

33
Q

Categoric variables

A

Have values that are labels

e.g. names of plants

34
Q

Continuous variables

A

Can take on any values (infinite number of values)

Given magnitude by counting or by measurement

35
Q

Control variables

A

A varaible which may, in addition ot the indepedent variable affect the outcome of the investigation and therefore has to be kept constant or monitored

36
Q

Dependent variables

Independent variables

A

The variable of which the value is measured for each and every change in the independent variable - it is affected by the independent variable

The variable for which values are changed or selected by the experimenter - affects the dependent variable

37
Q

Nominal variables

A

A type of categoric variable where there is no ordering of categories

38
Q

Reliability

A

Reliable experiments produce consistent and stable results.

39
Q

How does decreasing the time base of the oscilloscope reduce uncertainty?

A

Waveform will be stretched in the y axis

Resolution of the time axis increases

Increases the length/distance measured across the screen reduces percentage uncertainty in the reading of time

40
Q

Validated evidence

A

Data collected from an experiment used to test a theory

The results of the experiment are consistent and deemed reliable - they are able to be replicated/independently validated

41
Q

Things to consider when criticising data tables

A

Number of significant figures and consistency

Range of data used

Intervals used - are they consistent?

Number of values used

Number of repeats

42
Q

Fundamental SI base units

A

mass - kilograms (kg)

time - seconds (s)

amount of substance - mol

temperature - kelvin (K)

length - metres (m)

electric current - amperes (A)