Though ice cream is an excellent source of calcium, dairy farmers report that during the past ten years there has been a sharp decline in ice cream sales. And during the same period, sales of cheddar cheese have nearly doubled. Ttherefore, more and more people must be choosing to increase their intake of calcium by eating cheddar cheese rather than ice cream.
The reasoning above is most vulnerable to criticism on the grounds that it fails to consider alternative explanations of the decline in sales of ice cream.