Calcium content of salt

Use this diagram to motivate the use of normal distributions in the two groups as a possible population model.

The jittered dot plot is actually a 3-dimensional diagram. Drag the centre of the diagram towards the top left to rotate and display the two groups as histograms. (Or click the 3D rotation button.)

The histograms describe the distributions in the groups

Select Possible normal model from the pop-up menu at the top. This displays normal distributions that could be populations from which the data might have arisen.

Click Take sample to select random samples.

The model claims that the real data is such a random sample.


In the manufacture of chlorine, large quantities of raw salt containing impurities and various trace elements such as calcium and magnesium are dissolved in water to create a brine solution. The diagram shows calcium content (ppm) in salt samples from two different supply sources.