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Practical skills

Analysing results: anomalies and correlation

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Practical skills

The scientific method

How to plan experiments

Improving repeatability and reproducibility

Presenting results using tables and graphs

Analysing results: anomalies and correlation

Evaluating experiments

Modern analytical techniques II

NMR spectroscopy

Proton NMR spectroscopy

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Organic chemistry III

Benzene: structure and combustion

Electrophilic substitution

Friedel-Crafts reactions

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Aliphatic and aromatic amines

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Measuring rates of reaction

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Halogenoalkane reaction mechanisms

Activation energy and the Arrhenius equation

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Transition metals: electron configuration and oxidation number

Complex ions: formation, shape and isomerism

Colours of inorganic ions and complexes

Chromium and its reactions

Ligand substitution reactions

Transition metals as catalysts

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Electrochemical cells and redox

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The electrochemical series

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Redox titrations

Energetics II

Lattice enthalpies and Born-Haber cycles

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Enthalpy change in solution

Entropy and calculating entropy change

Gibbs free energy change

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Acids and bases

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The ionic product of water

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The equilibrium constant

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Equilibrium I

Reversible reactions

Le Chatelier's principle

Kinetics I

Collision theory and rates of reaction

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Hess's Law and enthalpy cycles

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Modern analytical techniques I

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Basic concepts of organic chemistry

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Alkanes and free radical substitution

Fractional distillation of crude oil

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Addition polymerisation

Halogenoalkanes and their reactions

Alcohol: classification and reactions

Oxidation of alcohols

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Acid-base titrations

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Group 2: ionisation energy and properties

Thermal stability of nitrates and carbonates

Chemical properties of Group 7

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Halide ion reactions

Testing for ions

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Calculating oxidation numbers

Oxidation, reduction and redox reactions

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Electronegativity and polarisation

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Hydrogen bonding

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The atom: history, structure and isotopes

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Periodicity

Explainer Video

Tutor: Sainab

Summary

Analysing results: anomalies and correlation

In a nutshell

When analysing results it's important to identify anomalies. Data can also be analysed visually using scatter graphs to see relationships between variables. However, correlation between two variables doesn't always mean there is a causal link.

Anomalies

Anomalous results are results which do not fit the trend seen with other values and are likely to be incorrect. These wrong values are likely to be due to random errors such as misreading apparatus. It is important to analyse your results and ask yourself if they make sense. Due to errors, anomalies are not included in any statistical analysis or when drawing lines of best fit.

Correlations

The relationship between the independent and dependent variables can be shown using scatter graphs which show the relationship between two variables.

Type of correlation	Graph	Description
Positive correlation		This is when one variable increases as the other increases.
Negative correlation		This is when one variable increases and the other decreases.
No correlation		This is when there is no relationship between two variables.

Correlation vs. cause

It is important to not jump to conclusions when assessing relationships. A correlation between two variables doesn't always mean a causal link. In experiments where all variables cannot be tightly controlled, such as experiments in nature, the change observed could be caused by a third variable.

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Length:

Unit 1

Presenting results using tables and graphs

Unit 2

Processing and presenting data

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Unit 3