Step 5: Hypothesis Statement
(will be worked on in class prior to due date)
Your hypothesis statement will be turned in during science class, reviewed by the teacher and returned. Below is a short explanation of a hypothesis statement and some examples of hypothesis statements.
Hypothesis statement--a prediction that can be tested or an educated guess.
In a hypothesis statement, students make a prediction about what they think will happen or is happening in their experiment. They try to answer their question or problem.
Question: Why do leaves change colors in the fall?
Hypothesis: I think that leaves change colors in the fall because they are not being exposed to as much sunlight.
Hypothesis: Bacterial growth may be affected by temperature.
Hypothesis: Chocolate may cause pimples
All of these are examples of hypotheses because they use the tentative word "may." However, their form in not particularly useful. Using the word does not suggest how you would go about proving it. If these statements had not been written carefully, they may not have been a hypotheses at all.
A better way to write a hypotheses is to use a formalized hypotheses
Example: If skin cancer is related to ultraviolet light, then people with a high exposure to uv light will have a higher frequency of skin cancer.
Example: If leaf color change is related to temperature, then exposing plants to low temperatures will result in changes in leaf color.
Example: If the rate of photosynthesis is related to wave lengths of light, then exposing a plant to different colors of light will produce different amounts of oxygen.
Example: If the volume of a gas is related to temperature, then increasing the temperature will increase the volume.
These examples contain the words, if and then. Formalized hypotheses contain two variables. One is "independent" and the other is "dependent." The independent variable is the one you, the scientist control and the dependent variable is the one that you observe and/or measure the results.
The ultimate value of a formalized hypotheses is it forces us to think about what results we should look for in an experiment.
Example: If the diffusion rate (dependent variable) through a membrane is related to molecular size (independent variable), then the smaller the molecule the faster it will pass through the membrane.
A hypothesis has classical been referred to as an educated guess. In the context of the scientific method, this description is somewhat correct. After a problem is identified, the scientist would typically conduct some research about the problem and then make a hypothesis about what will happen during his or her experiment. A better explanation of the purpose of a hypothesis is that a hypothesis is a proposed solution to a problem. Hypotheses have not yet been supported by any measurable data. In fact, we often confuse this term with the word theory in our everyday language. People say that they have theories about different situations and problems that occur in their lives but a theory implies that there has been much data to support the explanation. When we use this term we are actually referring to a hypothesis. For example, someone might say, "I have a theory about why Jane won't go out on a date with Billy." Since there is no data to support this explanation, this is actually a hypothesis. In the world of statistics and science, most hypotheses are written as "if...then" statements. For example someone performing experiments on plant growth might report this hypothesis: "If I give a plant an unlimited amount of sunlight, then the plant will grow to its largest possible size." Hypotheses cannot be proven correct from the data obtained in the experiment, instead hypotheses are either supported by the data collected or refuted by the data collected.
1. If I replace the battery in my car, then my car will get better gas mileage.
2. If I eat more vegetables, then I will lose weight faster.
3. If I add fertilizer to my garden, then my plants will grow faster.
4. If I brush my teeth every day, then I will not develop cavities.
5. If I take my vitamins every day, then I will not feel tired.
6. If 50 mL of water are added to my plants each day and they grow, then adding 100 mL of water each day will make them grow even more.