Does daily caffeine intake make subjects better at memory tasks? a study was conducted in which the daily habits of 30 college students were documented, focusing on how much caffeine they consumed in a week. after a week, the subjects were given a computer-based memory test on which they received a score on a 0 to 100 point scale. their scores were compared with how much caffeine they consumed that week.

select all that apply.

this is best described as an observational study.

the explanatory variable is the amount of caffeine consumed.

this study is best described as an experiment.

the explanatory variable is the score on the computer-based memory test.

the response variable is the score on the computer-based memory test.

the response variable is the amount of caffeine consumed.

A. This is best described as an observational study.

B. The explanatory variable is the amount of caffeine consumed.

E. The response variable is the score on the computer-based memory test.

Step-by-step explanation:

A) an observational study is a study in which a researcher observes the subject of interest without putting any control over them or without any intervention from a researcher.

This is an opposite of a random controlled investigation in which a researcher manipulate the process and see what the outcome will be after manipulation.

B)An explanatory variable is the variable that will give an explanation of the changes that are observed , it is anything that has an impact on the response variable. Amount of coffee consumed here will determine what response we would get from the participants in the memory test .

C) The response variable is the dependent variable , the test score above .

or

step-by-step explanation:

we need to solve for 'x' the following equation:  

we have that:

⇒

⇒ ⇒

factorizing, we get that:

  ⇒

then, the solutions are: or

nothing extraneous has been found!