Drawing & Interpreting Graphs
Chemistry: IB Diploma Higher Level, topic 7.2.1
Scatter Graphs
You should ignore outlying values that don’t fit with the general pattern. Outliers can move the line away from the rest of the values.
We can plot two variables against each other
Line of best fit
- The two variables are correlated if you can draw a straight line that lies close to most of the points.
- This line is called a line of best fit.
Correlation and line of best fit
- If it passes through almost all your points then there is strong correlation
- If the points don’t line up so neatly there is only weak correlation
- If it is not possible to draw a line of best fit then there is no correlation.
Positive correlation
- If the line of best fit slopes upwards the correlation is positive.
Negative correlation
- If the line of best fit slopes downwards the correlation is negative.
No correlation
- If it is not possible to draw a line of best fit then there is no correlation.
Scatter Graphs - Making Predictions
The line of best fit can be used to make predictions.
Interpolation
- Making predictions based within the range of the original data is called interpolation.
- It is more reliable than extrapolation because we know the pattern of data in this range.
Interpolation - predictions within the range of data
Extrapolation
- You can make predictions outside the range of data by extending the line of best fit.
- This is called extrapolation.
- Extrapolation is less reliable than interpolation because we cannot be sure the same pattern occurs in data outside our range.
Extrapolation - predictions outside the range of data
Test yourself on Drawing & Interpreting Graphs
What type of correlation does the following data have?
What type of correlation does the following data have?
What type of correlation does the following data have?
What type of correlation does the following data have?
What type of correlation does the following data have?