There are 4 equally sized glasses with the same amount of water in them. 2 teaspoons of sand are poured into the first glass, two teaspoons of sugar into the second glass, two teaspoons of salt into the third glass and two teaspoons of flour into the 4th glass. Each mixture is stirred for the same amount of time.

What am I measuring in the investigation (the dependent variable)?

The dependent variable in the investigation is not provided in the given information. If the investigation is to determine the effect of adding different substances to the same amount of water and stirring it for a given time, then the dependent variable could be the properties or characteristics of the resulting mixture such as the color, consistency, texture, taste, or odor. However, without further context or information, it is not possible to determine the dependent variable accurately.