Scientific Hypotheses

Definition of Hypothesis A tentative explanation for an observation, phenomenon, or scientific problem that can be tested by further investigation

1. Must be testable It is possible to gather data from observation and/or experiment about the hypothesis Example: Bean plants grow fastest when given fertilizer that contains potassium. Non-example: An alien life form causes catastrophic weather events.

2. Must be falsifiable The hypothesis can be shown to be false if in fact it is false. A scientific hypothesis is never proven — only disproven or supported. Example: My car won’t start because the battery is dead. Non-example: My car won’t start because of invisible rays from outer space.

Writing a good hypothesis If – then statements: If a dead battery is the reason my car won’t start then putting in a new battery will make it start. If bean plants grow faster when given fertilizer containing potassium then the beans with potassium-containing fertilizer will grow faster than beans grown with fertilizer that does not contain potassium.

Coin lab If a coin’s area affects the number of drops it will hold then

Writing your conclusion

1. Restate purpose of the experiment and your hypothesis The purpose of my experiment was to determine _______________________. My hypothesis was ___________________.

2. Indicate whether your hypothesis was supported or not and how the data supports your conclusion This experiment ______________________ (supports/does not support) my hypothesis. The data shows ______________________

3. Identify one or two possible sources of error and what could be done to correct for them next time My experiment was/may have been affected by _______________________________ In a further experiment it would be important to ________________________________

Now write a paragraph conclusion for the coin lab The purpose of my experiment was to determine … My hypothesis was … This experiment supports my hypothesis. The data shows … My experiment may have been affected by … In the future it would be important to correct this error by …

Completed conclusion The purpose of my experiment was to determine the effect of coin area on the number of drops the coin will hold. My hypothesis was that the dime would hold the least, followed by the penny, then the nickel, and the quarter would hold the most. Although data from individual trials varied from this somewhat, the median of the trials supports my hypothesis. A graph of the data shows a linear relationship between coin area and number of drops. My experiment could have been affected by vibrations that jarred the table. In a future experiment it would be important to make sure that no one walked around or bumped the table during the experiment.