+1 862 207 3288 The Scientific Method
1 An Example of Scientific Method
Theory in science is defined in The American Heritage dictionary as “systematically organized knowledge applicable in a relatively wide variety of circumstances, especially a system of assumptions, accepted principles, and rules of procedure devised to analyze, predict or otherwise explain the nature or behavior of a specified set of phenomena.” In other words, a theory is a unifying idea that explains and makes sense of a large body of repeated and repeatable observations.
Don’t assume that experiments and scientific studies are undertaken only by researchers in their laboratories. Once you understand how scientists observe, ask questions, make educated guesses as to explanations, and devise ways to determine whether their explanations are correct, you will be able to apply this and be able to design your own experiments.
For example, in our garden there is a beautiful and rare clematis plant with many flowers on it. I would like to take the seeds and grow additional plants to give my friends. I don’t know if seeds from these plants need to be exposed to the cold for a certain length of time or if they should be protected from our harsh northeast winters.
Prior research and observations that the hypothesis is based on: I search the library and gardening books for references and find that it is suggested that clematis can be propagated by planting seeds in autumn. I re-read pages 31-33 in Botany for Gardeners on requirements for germination. I observe, too, that the seeds on my plant are ripe and fall to the ground on their own in October.
Hypothesis: Clematis seeds need to be cold-hardened for successful germination.
(You may see hypothesis as “provisional conjecture” and you may also see it defined as “an educated guess.”)
Experiment: Collect seeds from the same clematis plant and divide them randomly into two groups. Put half in an envelope and leave undisturbed at room temperature in a dry location. This is the control group. Put half in an envelope and place in the freezer. This is the experimental group. The two groups differ by one variable only: that of temperature during the winter months. In the spring, when the ground is workable, plant sets of seeds in good fertile soil and determine germination rates.
Variable: The only variable is the temperature of the site where the seeds spend the winter.
They are collected on the same day, from the same plant, dried off for a few hours on the same paper towel, and separated and randomly put in identical envelopes.
To guarantee that the experimenter isn’t subconsciously biasing results, experimental design often ensures that the researcher herself doesn’t actually know which group is which, until after the results are in. This is referred to as a “blind study.” In the case of patients receiving an experimental drug, a “double-blind” study is designed so neither patients nor experimenters know who is receiving which treatment. In the clematis study, someone else chooses which envelope should go in the freezer and which stays at room temperature. The seeds are planted on the same day, in adjacent plots with identical soil conditions (e.g., pH, mineral content, nitrogen levels) and an identical watering schedule is used. Once seedlings emerge, the date is noted. Data also include germination rate (the number of seedlings that emerge divided by the number of seeds planted for the control and the experimental group).
Data: Let’s suppose I record these results:
Control group: 50 seeds. Ten germinated. 10/50= 20% germination rate.
Experimental group: 50 seeds. Forty germinated 40/50= 80% germination rate.
Conclusions: Overwintering in a freezer, rather than at room temperature, seems to improve germination rate.
Reproducibility: This experiment can be done again by anyone, or repeated again next year by the same experimenter.
New questions and possible new experiments: We can ask if there is a certain number of days that the seeds must be in the freezer and whether the exact temperature in the freezer has an important role. Experiments can be devised that have the number of days as a variable or that have the temperature of the freezer as a variable.
2 Observations of Nature as Scientific Method
Scientific experiments can be carried out in nature with methods that permit meaningful conclusions to be drawn from observations. We have just discussed scientific method and given an example of a study that could be done under laboratory conditions. In some of our readings (The Forgotten Pollinators, for example), scientific studies such as the field work of Luis Equiarte and Alberto Burquez involve observing nature in the wild.
For many nights throughout 1982-1994, Equiarte and Burquez observed “century plants” in the early evening after sunset. Their data consisted of the number of nectar-foraging visits by the lesser long-nosed bats. They tagged each flower stalk in order to be able to determine a possible correlation with the number of fruit set. They found that there was a direct connection between the bat visitation rates and fruit set and went on to draw some important conclusions and design further studies. (Click here if you are curious about century plants.)
You could design a similar study based on plants and pollinators found near you. Your hypothesis might be that tomato production per plant in your garden is related to the rate of pollinator visits. Your prediction might be that years with more pollinators will be years with more tomatoes and years with less pollinators (due to their own scarcity or weather patterns or human intervention) will result in less fruit. Is your hypothesis correct? You could design an experiment to test your hypothesis: observers could record the number of pollinator visits per plant and the number of fruits that develop. These are your data. Chances are that you would conclude that the success of your tomato crop is related to the availability of pollinators.
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