Chemometrics Flashcards
What is chemometrics?
- Computationally intensive
- Multivariate (many variables) statistical analysis
- Applied to chemical systems or processes
What can chemometrics do?
- Reduce complex datasets
- Identify and quantify sample groupings
- Optimise experimental parameters
- Isolate important variables and identify covariance
- Provide reproducible measures of data
- Allow for better visualisation of data
What is univariate?
Singular variable
What is the disadvantage of univariate?
Too simplistic approach for complex data
* wouldnt be able to see an outlier when using univariate
What is covariant analysis used for?
Used to explore relationships between different variables to look for patterns
What are the four chemometric categories?
- Design of Experiments
- Exploratory Data Analysis
- Classification
- Regression
What is Design of Experiments (DOE)?
- Used to work out which collection method might be best
- Relates to experimental setup
- Will affect evidence collection, storage, instrument selection, parameter optimisation
What is regression analysis?
- Based on y = mx + c linear relationship
- Maps the effect of multiple independent variables (predictors) upon dependent variables (respone)
- Allows prediction of quantitative sample properties
What is Exploratory Data Analysis (EDA)?
- Dimensionality reduction
- Pattern recognition technique - identify grouping
- Visualise trends that may otherwise have gone unoticed
- Determination of sample similarity in complex data
What does an unsupervised technique mean?
Exploring the data without any prior assumptions or knowledge of the samples
What is a supervised technique?
Building classification rules for known sample grouping (from EDA)
What are the two most commonly used EDA techniques?
- Cluster Analysis (CA)
- Principal Component Analysis (PCA)
What is Cluster Analysis (CA)?
- Unsupervised technique
- Samples grouped into clusters based on calculated distance (measure of their similarity)
- Either agglomerative or hierachical
- Output is a dendrogram
- Good intial technique - simplifies complex data
- Not limited to quantitative data
- Visualisation of relationships
- Can tell you that there are groupings but not why
What is agglomerative?
Taking individual samples and grouping them together to form clusters
What is hierachial (HCA)?
Opposite of agglomerative, taking a cluster and filter down into individual samples