Experimental Design Terms What are the things that a good scientific experiment includes?

Variables Something that can vary or change in an experiment

What are the variables? The time it takes to run a kilometer depends on the amount of daily exercise a person gets. The high the temperature, the faster an egg will cook. An investigation was conducted to see if keeping the lights on for different amounts of time affected the number of eggs that chickens laid.

Types of Variables Independent – changed by the experimenter (aka manipulated variable) Dependent – changes because of the independent variable (aka responding variable) Constants – things that stay the same in the experiment

Which is independent & dependent variable? The water temperature of water rises after calcium chloride is added The amount of pollution produced by cars was measured for cars using gasoline containing different amounts of lead. Lemon trees receiving the most water produce the largest lemons. The amount of algae growth in lakes seems to be directly related to the number of bags of phosphate fertilizer sold by local merchants. An investigation was performed to see if coen seeds would sprout at different times depending on the room temperature of the water in which they were placed.

Now you practice!!!! Identifying variables worksheet

Writing a good hypothesis What is a hypothesis? A tentative or trial solution to the question (must be testable) We will use an If…/then… statement Identify the IV and DV and plug them in. Make sure you predict what will happen to the variables Example: If the amount of lead in gasoline increases, then the amount of pollution increases.

Now you practice! Use the margin at the bottom of the identifying variables and write 5 hypothesis using the If…../then… format.

Control Part of the experiment that serves as the standard of comparison Necessary to detect the effects of hidden variables Hint: Try to leave out the independent variable Examples: Have unleaded gasoline in the previous experiment, not watering a plant

Repeated trials Reduce the possibility of chance or random errors during and experiment.

How can this experiment be improved? Most of the time students forget A control group Don’t have enough trials