L1 Craig: INTRODUCTION TO THE STATISTICAL ANALYSIS OF EXPERIMENTAL DATA Flashcards Preview

1st Year sem 2 : Forensic Analysis > L1 Craig: INTRODUCTION TO THE STATISTICAL ANALYSIS OF EXPERIMENTAL DATA > Flashcards

Flashcards in L1 Craig: INTRODUCTION TO THE STATISTICAL ANALYSIS OF EXPERIMENTAL DATA Deck (25):
1

what should uncertainty be estimated and quoted as?

error bar

2

what does uncertainty determine?

precision of the measured result

3

If you now the true value what can you do ?

measure ether accuracy

4

what is absolute uncertainty?

actual magnitude of the uncertainty

5

what is relative uncertainty ?

expressed as a fraction or percentage of the measured value e.g. Dx/x or 100 x Dx/x %

6

should the uncertainty be quoted to the same level of precision as the measurement itself ?

yes

7

what does it mean if no uncertainty is quoted?

last figure in the measurement is the best that can be determined
so uncertainty is half of this

8

what are the 2 categories of uncertainties ?

random and systematic

9

what's random uncertainty?

produces a scatter of values due to random effects such as poor resolution, electrical noise, human failings; for single measurement it must be estimated; for repeat measurements it may be calculated.

10

what is systematic uncertainty ?

arises through incorrect calibration or mistake in experimental design often resulting in an off-set value (bias); once identified it is often possible to correct for such an error.

11

why do we repeat measurements?

• Identify possible outliers–
• Calculate a mean
• Estimate the uncertainty

12

what are outliers?

values that appear way out of line and may be due to some one-off, gross error.

13

When only random errors are present the best-value is.....

average or mean

14

In practice often only a few (n < 12) repeat measurements are available. In this case the______ is a better estimate?

range method

15

what is standard error?

property of a set of measurements

16

what is standard deviation?

a population of numerical data through a statistical distribution

17

what des standard error depend on?

number of repeat measurements

18

what's median?

rank and its the middle value

19

what's mode?

most common value

20

why is standard deviation better than mean ?

enerally more useful as it is calculated with reference to the spread around the Mean value

21

what's the SD formula?

say it

22

whats the variance of data?

give by s^2

23

How to calculate relative standard deviation?

100 x S/mean %

24

what is RSD used to measure?

relative precision of different sets of measurements

25

does RSD have units?

no as its a ratio