Refer to the Minerals Engineering (Vol. 46-47, 2013) study of the impact of calcium and gypsum on the flotation properties of silica in water, Exercise 2.23. Recall that 50 solutions of deionized water were prepared both with and without calcium/ gypsum, and the level of flotation of silica in the solution was measured using a variable called zeta potential (measured in millivolts, mV). The data (simulated, based on information provided in the journal article) are reproduced in the table above and saved in the SILICA data file. Which of the two zeta potential distributions, without calcium/gypsum or with calcium/gypsum, is better approximated by a normal distribution?

Data from Exercise 2.23

A high concentration of calcium and gypsum in water can impact the water quality and limit mineral flotation. In Minerals Engineering (Vol. 46-47, 2013), chemical and materials engineers published a study of the impact of calcium and gypsum on the flotation properties of silica in water. Solutions of deionized water were prepared both with and without calcium/ gypsum, and the level of flotation of silica in the solution was measured using a variable called zeta potential (measured in millivolts, mV). Assume that 50 specimens for each type of liquid solution were prepared and tested for zeta potential. The data (simulated, based on information provided in the journal article) are provided in the table and saved in the SILICA data file.

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SILICA Without calcium/gypsum -47.1 -53.0 -50.8 -54.4 -57.4 -49.2 -51.5 -50.2 -46.4 -49.7 -53.8 -53.8 -53.5 -52.2 -49.9 -51.8 -53.7 -54.8 -54.5 -53.3 -50.6 -52.9 -51.2 -54.5 -49.7 -50.2 -53.2 -52.9 -52.8 -52.1 - 50.2 - 50.8 -56.1 -51.0 -55.6 - 50.3 -57.6 -50.1 -54.2 -50.7 -55.7 -55.0 -47.4 -47.5 -52.8 - 50.6 -55.6 -53.2 -52.3 -45.7 With calcium/gypsum -9.2 -11.6 -10.6 -8.0 -10.9 - 10.0 -11.0 – 10.7 -13.1 -11.5 -11.3 -9.9 -11.8 - 12.6 -8.9 - 13.1 - 10.7 -12.1 -11.2 - 10.9 -9.1 -12.1 -6.8 -11.5 -10.4 -11.5 -12.1 -11.3 -10.7 - 12.4 -11.5 -11.0 -7.1 -12.4 -11.4 -9.9 -8.6 -13.6 -10.1 -11.3 - 13.0 -11.9 -8.6 -11.3 –13.0 -12.2 -11.3 – 10.5 -8.8 - 13.4