Final answer:
The spread of control values can also be evaluated using the standard deviation, which provides a numeric measure of how data values are spread out from the mean. For skewed distributions, quartiles and box plots may offer better insights.
Step-by-step explanation:
In addition to the Gaussian curve, the spread of control values can be evaluated using the standard deviation. The standard deviation is a measure of how spread out the numbers in a data set are. If the standard deviation is large, the data points are spread out further from the mean and vice versa. For non-symmetrical distributions, other measures might be more helpful, such as looking at the quartiles, median, or using a box plot to understand the data's spread better.
It's vital to remember that variability in data can arise from different sources, including measurement, natural variation, induced changes, or sampling methods. To grasp the concept of variation and its nuances, it is often best accompanied by graphical representation of the data, like histograms or box plots which give a visual sense of the spread.