Ch 3 Types of Errors

Question 1

significant figures

Answer 1

the minimum number of digits necessary to express the results of aa measurement consistent with the measured precision

Question 2

uncertainty in measurements

Answer 2

-every measurement has unncertainty
-includes all digits known and the first uncertain one

Question 3

what is the uncertainty in the last digit assumed to be?

Answer 3

+/- 1 or +/- 0.001, unless specified otherwise

Question 4

what type of numbers are known with certainty so they don’t count?

Answer 4

integers and constants (FW, density)

Question 5

how is volumetric glassware measured?

Answer 5

to the hundreths

Question 6

what is the sig fig rule for addition and subtraction?

Answer 6

the answer has the same decimal place was the least precise (lowest sig figs) number

Question 7

what is the sig fig rule for multiplication and division?

Answer 7

the answer corresponds to number that has least number of digits

Question 8

what type of material lacks accuracy?

Answer 8

• beakers (500 mL)
  -based off sig figs not assumptions

Question 9

volumetric glassware

Answer 9

-flasks
-more accurate (500.00 mL)
-assumes 2 decimal places

Question 10

logarithms

Answer 10

retain only as many sig figs to the of the decimal as found in the no-exponential used to calculate it

Question 11

every measurement has some uncertainty, what is it called?

Answer 11

experimental error

Question 12

what is experimental error classified as?

Answer 12

systematic or random

Question 13

what are determinate errors?

Answer 13

-also know was systematic errors
-occur when something is wrong with the measurement

Question 14

what are the types of determinate errors?

Answer 14

-instrumental errors
-operative errors
-method errors

Question 15

instrumental errors

Answer 15

made by faulty equipment, uncalibrated glassware or weights

Question 16

operative errors

Answer 16

personal (human) error that can be reduced through experience with equipment, transferring solutions, etc

Question 17

method errors

Answer 17

incomplete or side reactions, impurities, or need for a blank

Question 18

what is a systematic error?

Answer 18

-consistent error that can be detected and corrected in theory
-many constant in direction and magnitude

Question 19

what is accuracy?

Answer 19

how close the number us to the true value

Question 20

what is the precision?

Answer 20

how many times you reproduce the same results

Question 21

what are indeterminate errors?

Answer 21

-also known was random errors
-errors that result from uncontrolled
-these errors have magnitude and direction
-not correctable and are always present
-follow a normal distribution of Gaussian curve

Question 22

what is absolute uncertainty?

Answer 22

-also known as standard deviation
-margin of uncertainty associated with a measurement
-manufacturer tolerance
based on precision
-has to match answer you have

Question 23

what is relative uncertainty?

Answer 23

-compared the absolute uncertainty with the size of the measurement
-based on the calculations

Question 24

how do you calculate the relative uncertainty %

Answer 24

(absolute uncertainty)/(magnitude of measurement) *100

Question 25

what is the relationship between magnitude and relative uncertainty %

Answer 25

-as magnitude increases the relative uncertainty decreases -larger the volume the smaller the RU

Question 26

what is addition and subtraction expressed as?

Answer 26

-standard deviations (abs uncertainty)

Question 27

what is multiplication and division expressed as?

Answer 27

by converting all tabs uncertainties to relative uncertainties

Question 28

what will happen if an experiment is repeated and the results are purely random?

Answer 28

the results will cluster symmetrically around the average value

Question 29

what is a Gaussian Distribution?

Answer 29

- aka normal distribution or bell shaped curve -the more times can experiment is repeated the more closely the results approach a smooth curve called GD

Question 30

what are the properties of the curve?

Answer 30

-the curve is symmetric (equal +ve and -ve errors) -small errors occur more frequently than large errors -the value that occurs most frequently is at 0sigma which represents the mean

Question 31

what does standard deviation measure?

Answer 31

the width of the Gaussian curve

Question 32

how is the mean and std dev represented for an infinite set of data

Answer 32

mean is represented as mu and std dev is represented by sigma

Question 33

true or false: 2/3rds of the measurements are expected to lie within one standard deviation

Answer 33

true

Question 34

-, 0,+1

Answer 34

68.3%

Question 35

-2, -1, 0, +1, +2

Answer 35

95.5%

Question 36

-3, -2, -1, 0, +1, +2, +3

Answer 36

99.7%

Question 37

expressing accuracy

Answer 37

measure accuracy in terms of its error

Question 38

what is absolute error?

Answer 38

-has units of measured value -u-X or u-xi

Question 39

wha t is relative error and how do you calculate it?

Answer 39

-compares the error to the size of the measurement -|u-xi/u|*100