Carlos, the president of a fraternity on campus, randomly sampled 500 students, asked them if they belonged to a fraternity or sorority, and asked them about their current GPA. He discovered that the GPAs of those people in fraternities and sororities were higher than those of people who were not involved in the Greek system. Gleefully, he presented his findings to the dean, saying that being involved in a fraternity or sorority leads to higher grades. What rule of research methods is Carlos breaking?

Correlation does not imply causation.

Explanation:

The rule 'correlation does not imply causation' means that just because there is a correlation between two variables it does not imply that they have cause-and-effect relationship between them.

The terms causation and correlation are oftenly used interchangeably in wrong sense of understanding.

The term correlation simply implies that there is a relationship between two variables and does not inform about hows and whys. Whereas, the term causation helps to understand the cause of change in one variable that leads to changes in another variable as well. This is also known as cause-and-effect relationship.  

The rule that Carlos is breaking in his research is that he is trying to prove a cause simply because they show a correlation between the variables. The rule of correlation does not imply causation; thus the correct answer.

the technology changed agriculture in an impacting manner since many people left the field work by a cellular or other technological appliances

changes in factors like average income and preferences can cause an entire demand curve to shift right or left. this causes a higher or lower quantity to be demanded at a given price. demand curves relate the prices and quantities demanded assuming no other factors change. it is important for consumers to know this information, because it is crucial for them to know what they can afford and can't afford. i hope this .