3.12 Estimating Slope with Variable Data

Just like when you learned about level, variability makes it more difficult to estimate the slope. When the data are really variable, you can’t just visualize a line that connects the first data point to the last data point to estimate the slope. This is a good starting place, but you have to look closely at how the other data points in the phase are moving over time, as well. This is similar to the band that you used to estimate the level. Let’s start thinking in terms of a band to estimate the slope, as well. Look at this graph. We are teaching this young girl how to make a sandwich and this graph shows the number of steps she completes accurately and independently each day. What is the slope?