Quantative Analysis_Lecture 3: Error Analysis

Front 1

Compare accuracy and precision?

Back 1

Precision: Closeness of results that have been obtained in the same way

Accuracy: the closeness of the measurement to its true value or accepted value.
-it can NEVER be exactly because true value is never exactly known.

Front 2

What statistical calculations are used to determine precision?

Back 2

1. Standard deviation

2. Variance

3. Relative Standard Deviation (RSD)

4. Coefficient of Variance (CV)

Front 3

What statistical calculations are used to determine accuracy?

Back 3

1. Absolute error = u - x

2. Relative error = (u - x)/u

Front 4

What are the causes of systematic error?

Back 4

1.interference: e.g. due to sample itself, temp, etc

2. Sampling error: e.g. bubbles in pipets

3. Error in standards or control

4. Old/bad reagents

5.Wrong instrument setting

6. Electrical interference

7. Instrument design - doesn't do what it suppose to do.

8. Personal bias

9. chemical purity

Front 5

What are the cause of random error?

Back 5

Causes: affecting one sample per run.
1. Sample collection

2. Sample preservation problem

3. Sample transport problem

4. Sample storage problem

5. Calculation error

6. Reporting results e.g., 1.0 --> 0.1 reported

Front 6

List three measures of central tendency?

Back 6

Central tendency are statistics that represent some central value around which the data is distrubuted.

1.Mean
2. Median
3. Mode

Front 7

How to find median for odd set?

Back 7

Odd set, n = total
1. order highest to lowest

2. n+1

3.divide by two

4.position = median value

Front 8

How to find median for even set?

Back 8

Even set, n= total
1. order highest to lowest

2. n/3

3. +1

4. Median is average of (n/2) and (n/2 +1)

Front 9

Describe the types of errors that exist in measurements.

Back 9

1. Systematic error (determinate)
-affect accuracy, assign cause, same magnitude

2. Random (indeterminate)
-affect precision, no pattern, uncontrollable

3. Personal errors
- mistakes, carelessness, inattention, and prejudice

4. Gross errors
- Outliers