Now that we have learned some of the language needed to speak chemistry, we now need to discuss the process by which we will investigate the chemistry and crimes presented in this course and its lab. The scientific method is used to produce systematically reliable results and conclusions when investigating any scientific material. The investigation always starts with a simple question. How does this work?, why does this happen?, how much is produced,? Where does this go?, etc. Once you have established the question, you need to discover as much as possible about what is already known. This research is necessary to avoid redundant work and will help to form the parameters of the next step in the investigation – the hypothesis.
The Hypothesis
A hypothesis needs to be logical, must use precise language and should be testable with research or experimentation.
Question: Does the amount of preservatives in our food increase the amount of time required for a body to decompose?
Hypothesis: The rate of decomposition of the human body is directly related to the quantity of preservatives consumed in life.
The hypothesis is a clearly stated summary of what "question" is being asked and what the expected outcome of the investigation will be. The hypothesis should be written so that is can be tested and it should be written as precisely as possible. A hypothesis can be positive or negative in its statement. For example, you may have heard the statement that modern tables of decomposition have needed adjustment due to the amount of preservatives we have in our food these days. This statement may or may not be an "urban legend". So if we were to ask a question, it would be "does the amount of preservatives in our food increase the amount of time required for our bodies to decompose after death?" If we rephrase the question into a hypothesis, we might say in a positive manner that "The rate of decomposition of the human body is directly related to the quantity of preservatives consumed during life" or in a negative manner, "The rate of decomposition of the human body is not directly related to the quantity of preservatives consumed during life". Once we have established our hypothesis we then need to determine the experimental steps to take to determine the validity of our hypothesis.
Testing the Hypothesis
Possible ways to test the hypothesis:
- Use mice or other animals
- Exhume bodies from rural areas of the world where processed foods are not used
- Get elderly/dying volunteers and determine the amount of preservatives in their diet. Follow their decay after death
- Observe the decay of several bodies and chemically test for preservatives in their tissues
Testing a hypothesis provides the most challenge to a researcher. The hypothesis we have just stated is that there is a direct relationship between the amount of preservatives consumed and the rate of decomposition. The question is how to test this hypothesis. I am pretty sure we can’t just feed a group of people a lot of twinkies and then kill them and watch the rate of decay so we need to be more clever than that. The test we use needs to have "controls". Controls are rules that we impose on the tests so that the experiment will be reproducible. Controls can be as simple as comparing all data at the same temperature to as complicated as selecting subjects that have the same genetic background which of course would require intense preparatory testing. Deciding on a test for our hypothesis will be based on these controls as well as the time and often the money available to run the tests. Here are several ways to test the hypothesis, each of which have both merit and also control problems.
1) We can use mice or another animal. Feed one group food containing preservatives and another food without preservatives, euthanize the mice and then watch the decay rates. While this method allows for the control of the amount of preservatives, it does not necessarily correlate well to a human being consuming these foods for a lifetime. 
2) We could also get permission to compare the rates of decomposition for bodies that are from areas of the world that do not consume foods with preservatives to those that do, but what if one of the bodies we exhume from the US is a health nut and never ate a Twinkie? This might give us bad information. 
3) Another idea would be to make a long term study of elderly or dying people and survey them about their eating habits. Once they die we could then observe the decay rates and compare them to the amounts of preservatives they ate. This of course could be a really long term study and would depend on the subjective memories of the individuals involved, making control of the experiment difficult. 
4) Finally, perhaps a better way to go about the experiment that would not require the long period of time or the involvement of subjective data or even animal testing would be to chemically test bodies that were already in decay. This would allow other controls such as temperature and humidity etc. to be applied and by testing the tissues of the bodies get real values as to whether there were preservatives present in the tissues or not. But again there might be other issues that could not be controlled such as what types of preservatives were consumed or how much bacteria each body had in their intestines which would increase or decrease the rate of decay. But that would lead to the next step in the process – analysis and conclusions.
Analysis and Conclusions
Once all of the experimental data both qualitative and quantitative is collected, it must be processed and analyzed. Process of data could mean converting the data from one form to another. For instance you measured the mass and volume of the substance under study but you really need the density so you must calculate that value using the data you collected.
It could also mean simply collating a large amount of data. For instance if you interviewed 700 men regarding the sport(s) they watched over a weekend you would need to put the answers into a spreadsheet and "collect" the data so it can easily be read and patterns found.
Data collected: hours of sports watched by men in 48 hours
Once the data has been processed and analyzed, conclusions regarding the validity of the hypothesis are made. These answers to the question(s) that have been asked should be stated as either supporting or denying the basic hypothesis as it was stated. Returning to our hypothesis regarding decomposition, say hypothetically that after running a series of chemical tests on a large number of bodies we found the following data:
Based on analysis of the information shown in the table, there does seem to be a difference in the time each stage of decomposition started with each concentration of preservative, but the results do not form a consistent trend since the 0.5-.75% data seems to drop rather than continue to rise. So the data collected lead to an inconclusive result. While some of the data do seem to indicate that the decay rate is related to the preservative amount, other data do not. What do you do in this case? Well, the easy answer is start over. Use the information to build a better test and/or rephrase the hypothesis to be a more precise statement. This is the cycle of the scientific method. If and when you do confirm the hypothesis, you would then report that information in a publication or report. Until then you continuously, hypothesize, test and rethink your work until a conclusion can be drawn.