Independant, dependant, control variable - experiment?

we doing an experiment in school, to see how coke and diet coke affcts our reactions. so 1 person is going to hold a ruler and drop it, the ptherperson after drinking coke tries to catchthe ruler?Independant, dependant, control variable - experiment?
And what is the goal of the experiment?


To see if coke and diet coke affects reaction time or something else?


Let's assume that you are checking on reaction time when ingesting caffeine, and what the differences are between drinking coke and drinking diet coke.





When you conduct a scientific experiment you need a control to determine what is actually happening (you factor out this variable or you adjust for it). In this case you need a subject who has taken diet coke (subject 1) a person who has taken regular coke (subject 2) and a person who hasn't drunken any cola; the control (they should drink water in a dark opaque glass so the observers don鈥檛 know what they have drunken, not what brand of coke or even if it was coke). Before hand you should test the reaction time of each person and try to get those with the same or very similar reaction times. This way the reaction time doesn't become a variable, or at least it is a variable under your control. What you are testing is the change in reaction time and that is the dependent variable.





The amount of coke and diet coke consumed is controlled, and this is what is being tested--the effect that taking this much coke has on your reaction time. The control subject doesn't drink any coke so you can tell the difference that each coke had alone. Control subjects help to remove the human variable from the equation. Does a person THINK they have better reaction time after drinking coke or diet coke, and does the act of drinking something affect reaction time?





Now you are testing the diet coke vs. the regular coke and vs. water (your control). In the case of Coca Cola brand Coke Zero and Diet Coke both have caffeine, but of different amounts than regular coke. The goal of the experiment is to see how much effect caffeine has on a person's reaction time (the time and distance it takes to catch a ruler).





You want to use a 1'-0'; (or 1 yard) ruler and have the other person hold their hand several inches down the side of the ruler so they can grab it as it falls. The time between dropping it and the other person catching it is their reaction time and this can be seen as the distance that the ruler fell as well as the timed interval done with a stopwatch; and you will need an extra person to time this interval (the same person should time it for each experiment each time). The time difference between each subject should be measured several times and ideally you should have more than just three subjects. You should have say 15 subjects; 5 drinking diet coke, 5 drinking normal coke and 5 not drinking coke. You should test the subjects鈥?reaction time before the experiment and during the course of the experiment. You should use the same person to do the testing each time so that their own reaction time (the time it takes to press the stop watch) is a constant factor and not a variable and therefore can be ignored. Then you can conduct the experiment 4 times for each person to test the effects over a period of time. In this case you would list the results add them up, for each person, and average them by dividing the number by 5 (the number of experiments) for each person and then take the final averages and average them by 4 to arrive at a total average for each category (good experiments involve lots of repetition and have repeatable results) That would give you a mathematical average. Or you could not average the results by 4 and say that this is the difference between each time interval.





You need the timekeeper to keep the same time and for their reaction time to be independent of the experiment. Ideally, you should substitute a machine to time the distance of the ruler drop. This lets you ignore their reaction time.





The dependent variable is the amount of time that changes (between drinking each coke and between the type of cokes drunk) since you are averaging it and testing among several people you will get an average value that is closer to the true value of your dependent variable. Your control is the subjects who don't drink and the variables under your control will be the time keeper's reaction time (time to press the stopwatch on and off) and what they drink.





The regressor would be the distance that the person holds the ruler from the person who drops it. Ideally, each ruler drop should be done by one person and timed with one timekeeper to keep their variables out of your experiment. One old bar trick is to hold a dollar bill and have a person hold their fingers close to it and try to catch it as you drop it. If that person is drunk then their reaction time may decrease, but the true trick is for you to hold the dollar bill close to their fingers so that normal human reaction time is not enough for them to catch the bill. This is why you need a longer ruler, so the subjects of the experiment will have more time to grab the ruler. You need to run the test several times to see the cumulative effect of each drink and each drink should be of the same size. You should also have the person drink the coke (or not) and then wait 5 minutes and test them, then wait 5 more minutes and test them again and wait another 5 minutes and test them a third time and so on. This how your experiment can account for the time it takes for the caffeine to be absorbed by the body. Ideally, you would continue for 20-30 minutes at five minute intervals to allow for each person's different blood chemistry to absorb the coke and you should do this when they have an empty stomach. But, you may not have control over that or the time to do the experiment so many times. It is important to tell your teacher and subjects that the more data you collect the higher your accuracy.





Finally you need to make sure that each person drinking the coke doesn't know if it is diet or regular coke so that factor won't affect the test and ideally the people conducting the experiment should not know the difference either; this is called a double blind experiment. It is the standard held to for drug companies when they do tests. You can do this fairly simply by concealing the brand of cola with paper. Some people can taste the difference so you want to try and get test subjects who don't notice or have trouble determining the taste difference. You want to remove the variable that they may THINK that their reaction time changes with each type of coke that they drink (this is the blind part of the test). You want to prevent the experimenters to show their own bias by making them blind to the type of drink consumed (hence the phrase double blind test). To do that in idea circumstances you should have all your subjects drink something in a glass that can't be seen through, with 1/3 of your subjects just drinking water. Even a simple experiment like this one can have a lot of variables in it.





According to Wikipedia: http://en.wikipedia.org/wiki/Dependent_a鈥?/a>


';Dependent variables and independent variables refer to values that change in relationship to each other. The dependent variables are those that are observed to change in response to the independent variables. The independent variables are those that are deliberately manipulated to invoke a change in the dependent variables. In short, ';if x is given, then y occurs';, where x represents the independent variables and y represents the dependent variables.





Depending on the context, independent variables are also known as predictor variables, regressors, controlled variables, manipulated variables, explanatory variables, exposure variables, or input variables.





The dependent variable is also known as the response variable, the regressand, the measured variable, the responding variable, the explained variable, the outcome variable, the experimental variable or the output variable.';