Interpreting Graphs 7

To read a value from a graph, draw a line from the known value on one axis to the line or curve, then across or down to the other axis. Use a ruler and read to the nearest half of a small square.Interpolation is estimating a value that lies between measured data points. It is fairly reliable because it is within the range of the data.Extrapolation is extending the line beyond the measured data to predict a value outside the range. It is less reliable because the trend may not continue, for example an enzyme may denature at higher temperatures.An intercept is where a line crosses an axis. For example, in an investigation of osmosis, the concentration of sucrose where the line for percentage change in mass crosses the x-axis (no change in mass) gives the solution with the same water potential as the tissue.When quoting values from a graph, include the units and use the scale carefully.