This tutorial is about using logical comparisons in a sentence. We should compare only equivalent concepts. Don't compare something to a group its part of without including 'other' or 'else'. Be clear about what you are comparing. The comparisons must be between apples to apples (i.e. between objects or things of same group). If they are not then you fix the problem by:-1. Repeating the apples. 2. Using 's or that or those. 3. Reworking the sentence. To demonstrate this take the following example.Her prom dress was as glamorous as a movie star on the red carpet. (This sentence construction is wrong as dress is compared to movie star.) This can be set right by the following methods:-1.Her prom dress was as glamorous as the dress of the movie star on the red carpet. (Comparing apple to apple that is dress to dress).2.Her prom dress was as glamorous as that of a movie star on the red carpet. (In this case dress is compared to that of the movie star.)3. In her prom dress she was as glamorous as the movie star on the red carpet.(in this case she is compared movie star.)So the wrong sentences can be corrected in the 3 forms shown above.