Steel Works Slag data.

It is difficult to get information from an unsorted numerical list. Sorting makes it easier to understand the distribution of values.

After sorting, ask the students whether they see anything unusual. Click Answer to highlight the gap in the middle of the distribution; discuss the possibility of two distinct clusters.


Click Show dot plot to display the data graphically. Explain that the graphical display shows distribution better than sorted list.

The dot plot and list of values are dynamically linked so clicking crosses highlights the values in the list (and vice versa).

In steel works, iron ore is smelted to extract as much iron as possible, but some iron remains in the waste from the process (slag) in the form of iron oxide (FeO). The data set contains the percentage of FeO in slag sampled from 20 batches of iron ore. The initial list shows the values in the order collected.

(Further investigation showed that the ore came from two different sources that largely coincided with the two clusters.)