Tips for Writing a Hypothesis
   
   
(1) From Topic to Expert
   
At this point you have chosen a topic to research further and become an expert on. Take for example "I want to compare the effectiveness of natural insect repellents and chemical repellents."
   
The research process should teach you about what repels insects, how natural insect repellents work, how chemical repellents work, how insects respond to different types, and how successful and effective each is. Keep in mind that probably not all insects will react to the same repellent in the same way.
   
   
(2) Background on a Hypothesis
   
Your hypothesis outlines what you are going to test and what you expect to happen. It guides you in building your experiment, so building a strong hypothesis will save time and confusion later.
   
Your hypothesis describes how you are treating the groups you want to experiment with (your independent variable, IV) and what you expect to happen (your dependent variable, DV).
   
In the repellent example, you are controlling the types of repellent (IV), so you'd choose a specific brand, blend, or concentration to test. Maybe you choose to have one homemade blend of natural repellent where you change the amounts of ingredients to see how its effect changes. Or maybe you compare one brand of natural repellent to a brand of chemical repellent. What you compare is up to you, and it will drive how you build your experiment.
   
Once you've decided what you want to compare, you will need to measure the outcome (DV). In the repellent example, how would you measure "effectiveness"? Would you count flies, ants, or other insects? Would you measure how close a they get to a sample of the repellent? Would you count how many come within a certain distance of a sample of repellent?
   
   
(3) Building your Hypothesis
   
Your hypothesis will have three pieces strung together. Your independent variable here is repellents, and your dependent variable is ants. Take the example:
   
A sponge soaked in lemon eucalyptus attracts fewer ants than a sponge soaked in DEET.
 
  (I) The first part identifies the group you are experimenting with (your IV, "lemon eucalyptus"), and how you are controlling it ("sponge soaked").
 
  (II) The second part identifies the result you expect (the change in your DV, "fewer ants").
 
  (III) The third part adds the other group that you are comparing against (your other IV, "DEET") being controlled the same way ("sponge soaked").
   
   
(4) Using a "Control"
   
In some cases you'll be testing the same object, but with different treatments. Here, the independent variable in the third part will be the same as the first part, but nothing is added to it or changed. We call this the "control". For example
   
A basil plant whose leaves are sprayed with sulfuric acid will grow shorter than a basil plant whose leaves are not sprayed with anything.
   
In both cases you are measuring the height of the basil plant, but one of them is being sprayed with sulfuric acid, and the other is not having anything done to it. The second one is the control.
   
   
(5) Example Hypotheses (plural ends in -es)
   
Comparing weak hypotheses to strong ones
   
(a) Weak: "Candle color affects how long a candle burns."
   
  Strong: "Paraffin wax candles with colors added to them do not burn as long as paraffin wax candles with no colors added to them."
   
  Explanation: The second is stronger because you are specifying the type of wax you want to burn. There are many different types of wax, and some, like beeswax, are not naturally white. Comparing the burn times of different types of wax would be a different experiment. In the second you are also specifying the outcome of the test, that the sample with colors will not burn as long as the other, whereas the weak one only says that it will "affect how long", but doesn't say in which direction, more time or less time.
   
   
(b) Weak: "Dishwashing detergent makes plants grow less."
   
  Strong: "Basil planted in soil with dishwashing detergent added to it will grow shorter than basil planted in soil with no detergent."
   
  Explanation: The second one is stronger because you specify which species of plant you are going to test, where you are going to add the detergent, and what aspect of growth you are going to measure (height, as opposed to leaf size). So when it comes time to prepare your experiment, you have most of your decisions made about materials and procedure. You'll still have to choose which brand and type of dishwashing detergent to use, but you could have several pots, each testing several a different dishwashing detergent against the control.
   
   
(6) Conclusion
   
It takes time to craft a strong hypothesis, but the hard work you do early on will save you time and effort and keep you more focused when it comes to testing.