Analysing graphical data
A graph helps to analyse data and can be used to draw a conclusion:
- choose axis scales so that the plotted points occupy at least half the space available (this will help make the graph easier to read)
- label both axes, including the units
- think about whether the line should pass through the origin (0,0)
- choose regular intervals along the scale that make it easy to plot the points and read off values, eg increments of 2, 5 or 10
- a point that is not near the best fit line is odd (or anomalous) - it needs to be explained before it can be ignored
- after plotting the point, draw a line of best fit - remember this can be curved
Reading the shape of a graph
A lot can be learnt by looking at the shape of a graph. The Another word for steepness. On a graph, the gradient is defined as being the change in the 'y' value divided by the change in the 'x' value. It defines how steep a line is. is the slope of the graph. When looking at a graph of mass produced against time, the gradient of the graph shows the mass produced per second. This is the A measurement of how quickly a reaction takes place..
Finding more data from a graph
Finding values within the range originally measured is called Reading a pair of values on a graph that lie between plotted data points..
To interpolate a graph, read up from the horizontal axes, then across to find the new value.
Finding values beyond the range that was originally measured is called Extending the line on a graph in order to estimate values that lie beyond the plotted data..
To extrapolate a graph, first extend the line. Then read up from the horizontal axis and across to find the new value.