Module 3

Question 1

Characterization of systematic, Random and gross errors

Answer 1

Systematic: determinate, affects accuracy, 1-sided
Random: indeterminate, affects precision, 2-sided
Gross: affects accuracy and precision

Question 2

Errors affecting accuracy (systematic errors example)

Answer 2

Sampling, method, measurement, personal

Question 3

What are sampling errors and how to mitigate

Answer 3

If improper or non representative sample is collected and analyzed
Non homogenous sample leads to inaccurate results
Mitigate by collecting true representative sample

Question 4

What is a method error and examples how to mitigate

Answer 4

Result of non ideal behaviour of reagents and reaction
Incompleteness of reactions, instability of some species
Mitigate by parallel analysis of samples by an independent method

Question 5

What are measurement errors and how to mitigate

Answer 5

Instruments not calibrated properly
Mitigated by calibrating instruments

Question 6

What are personal errors how to mitigate

Answer 6

Lack of judgement. Ex. Level of liquid, Color of solution at endpoint
Mitigate with more care and paying greater attention to detail

Question 7

What are random errors caused by and how to treat

Answer 7

Caused by uncontrollable variables that exist in every physical or chemical measurement
Treated by statistical analysis of dataset

Question 8

What 2 components must any measurement have

Answer 8

1) a numerical value
2)a degree of uncertainty

Question 9

What is uncertainty

Answer 9

The range of values within which the value of the analyte can be said to lie within a specified level of confidence

Question 10

What is range of measure of

Answer 10

The scatter of the data rather than precision

Question 11

What is Standard deviation and what is it not

Answer 11

How closely the data is clustered around the mean
It is not the random error of the mean
A measure of uncertainty of the mean due to random error

Question 12

When does a Gaussian distribution occur

Answer 12

When an experiment is repeated and the results approach a smooth curve

Question 13

What is the coefficient of variation and the formula

Answer 13

Relative standard deviation
RSS= sd/meanx100

Question 14

What is a confidence interval and equation

Answer 14

A range of values within which is there’s a specified probability of finding the true value
CI=mean +/- txSD/(n)^1/2

Question 15

What does range depend on

Answer 15

Precision of individual measure,ents
Number of measurements made

Question 16

What are outliers and how to identify

Answer 16

A measurement in dataset that’s distinct from all other measurements
Identify with Grubb’s test or Dixon q test

Question 17

What is significance testing

Answer 17

Significance testing determines if the difference between two values is too large to be explained by indeterminate error

Question 18

Steps to significance testing

Answer 18

1. State experimental problem as yes or no question
2. A null hypothesis and an alternative hypothesis provides answers to question
3. T test is preformed to see if there’s a statistically significant difference
4. A confidence level is chosen to decide if null hypothesis is accepted or rejected

Question 19

What is a null hypothesis

Answer 19

States the mean values from two sets of measurements are different

Question 20

What is an alternative hypotheses

Answer 20

States the mean values from two sets of measurements are different