Making Connections Lab Procedure
In an experiment, we need to control as many potential variables as possible (within reason). In this case we want to test if exercising before squeezing a clothespin (experimental group) will result in more or fewer squeezes per some amount of time as compared to not exercising before (control group). The independent variable is what you, as the researcher, will vary: the amount of exercise. The dependent variable is what you will measure: the number of squeezes.
The Procedure:
Each researcher is required to gather data for 3 different subjects.
1. Gather subjects, a clothespin, and some method of keeping time to the seconds. Different clothespins will have different spring tensions and therefore you need to use the same clothespin before and after exercise for a given person. Yes, the clothespin will wear down (2nd law of thermodynamics) and become easier to squeeze, but this is the best we can do with the materials we have.
2. The subject should not have exercised that day. Have the subjects sit down and rest for 10 minutes to get rid of any waste products that might be in the muscles and make sure they are completely oxygenated. Of course there are other variables and you can get real crazy with this. For example, the temperature of the room, the humidity, what the subject has eaten, the time of day, etc…but we will do what we can.
3. After resting 10 minutes, the subject will squeeze the clothespin as many times as possible in one minute. Very important is that the subject should use their strong hand (right hand if they are righty; left hand if they are lefty) and everyone needs to press the clothespin the same exact way. Remember, you are trying to eliminate doubt in your results. If they squeeze it differently, one can argue that this is the reason you saw a difference between the groups and not the fact that they exercised or not. I suggest they use only the index finger and thumb, and the other fingers are held up and away from the clothespin like giving the “everything’s OK” sign. Basically, no fingers should touch their pointer or thumb. Make sure the squeezes are all the way until the wood touches on both the open and the close.
4. Count as carefully as you can the number of clothespin clicks. Two or more people should count to get as accurate a measurement as possible.
5. After this, the subject’s fingers are obviously fatigued and this cannot be a factor in the experiment. Therefore, the subject must be allowed to rest at least for a day.
6. The next day, the subject should come back and rest for 10 minutes again so that the 10-minute rest is not a possible variable. They should then exercise for two minutes. The exercise needs to be the same for everyone. There will obviously be variability in the exercise. For example, if we say to do jumping jacks, not everyone will expend the same amount of ATP by doing the same number of jumping jacks in the same amount of time and even this wouldn’t work since all our arms/legs/etc… have different masses. Again, we do the best we can. Let’s make the exercise jumping jacks for two minutes.
7. Immediately following the exercise, the person should start squeezing and counting should be conducted as discussed in number 4.
8. Make sure you write the data and post it to edmodo.com when you are finished. Everyone will pull the data from there.
9. Again, there are many aspects in this experiment that we cannot possibly control. One of your jobs is to be aware and write about them in your manuscript (All experiments have faults, even those done by professional scientists. Nothing is perfect.). There are also a number of sources or error, both human error and systematic error. We will discuss these different types of error in class. You will also need to write about these.
Your job as a scientist is to scrutinize your own experiment before you perform it otherwise other people will after you are done. Minimize doubt in your results!! Think over any other explanation for what you observe and design your experiment to minimize the number of these explanations.