Understanding Simple vs Controlled Experiments

Understanding Simple vs Controlled Experiments An experiment is a scientific procedure used to test a hypothesis, answer a question, or prove a fact. Two common types of experiments are simple experiments and controlled experiments. Then, there are simple controlled experiments and more complex controlled experiments. Simple Experiment Although the phrase simple experiment is tossed around to refer to any easy experiment, its actually a specific type of experiment. Usually, a simple experiment answers a What would happen if...? cause-and-effect type of question. Example: You wonder whether a plant grows better if you mist it with water. You get a sense of how the plant is growing without being misted and then compare this with growth after you start misting it. Why Conduct a Simple Experiment?Simple experiments usually provide quick answers. They can be used to design more complex experiments, typically requiring fewer resources. Sometimes simple experiments are the only type of experiment available, especially if only one sample exists. We conduct simple experiments all the time. We ask and answers questions like, Will this shampoo work better than the one I use?, Is it okay to use margarine instead of butter in this recipe?, If I mix these two colors, what will I get? Controlled Experiment Controlled experiments have two groups of subjects. One group is the experimental group and it is exposed to your test. The other group is the control group, which is not exposed to the test. There are several methods of conducting a controlled experiment, but a simple controlled experiment is the most common. The simple controlled experiment has just the two groups: one exposed to the experimental condition and one not-exposed to it. Example: You want to know whether a plant grows better if you mist it with water. You grow two plants. One you mist with water (your experimental group) and the other you dont mist with water (your control group). Why Conduct a Controlled Experiment?The controlled experiment is considered a better experiment because it is harder for other factors to influence your results, which could lead you to draw an incorrect conclusion. Parts of an Experiment Experiments, no matter how simple or complex, share key factors in common. HypothesisA hypothesis is a prediction of what you expect will happen in an experiment. Its easier to analyze your data and draw a conclusion if you phrase the hypothesis as an If-Then or cause and effect statement. For example, a hypothesis might be, Watering plants with cold coffee will make them grow faster. or Drinking cola after eating Mentos will cause your stomach to explode. You can test either of these hypotheses and gather conclusive data to support or discard a hypothesis.The null hypothesis or no-difference hypothesis is especially useful because it can be used to disprove a hypothesis. For example, if your hypothesis states, Watering plants with coffee will not affect plant growth yet if your plants die, experience stunted growth, or grow better, you can apply statistics to prove your hypothesis incorrect and imply a relationship between the coffee and plant growth does exist.Experimental VariablesEvery experiment has variables. The key variables are the independent and dependent variables. The independent variable is the one you control or change to test its effect on the dependent variable. The dependent variable depends on the independent variable. In an experiment to test whether cats prefer one color of cat food over another, you might state the null hypothesis, Food color does not affect cat food intake. The color of the cat food (e.g., brown, neon pink, blue) would be your independent variable. The amount of cat food eaten would be the dependent variable.Hopefully, you can see how experimental design comes into play. If you offer 10 cats one color of cat food each day and measure how much is eaten by each cat you might get different results than if you put out three bowls of cat food and let the cats choose which bowl to use or you mixed the colors together and looked to see which remained after the meal. DataThe numbers or observations you collect during an experiment are your data. Data are simply facts.ResultsResults are your analysis of the data. Any calculations you perform are included in the results section of a lab report.ConclusionYou conclude whether to accept or reject your hypothesis. Usually, this is followed by an explanation of your reasons. Sometimes you may note other outcomes of the experiment, particularly those that warrant further study. For example, if you are testing colors of cat food and you notice the white areas of all the cats in the study turned pink, you might note this and devise a follow-up experiment to determine whether eating the pink cat food affects coat color.