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 higher 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 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 corn 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 explanation 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.

Write a good hypothesis The temperature of water rises after calcium chloride is added The amount of algae growth in lakes seems to be directly related to the number of bags of phosphate fertilizer sold by local merchants. Lemon trees receiving the most water produce the largest lemons.

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

A study was conducted to determine how the number of paper clips picked up was related to the number of batteries connected to the electromagnet. The magnet connected to 1, 2, 3, 4, or 5 D Cells, was placed on the top of a pile of 100 paper clips and lifted. Identify 2 constant variables Identify the independent variable. Identify the dependent variable State the hypothesis being tested.

Experimental Design Terms (2) What are the things that a good scientific experiment includes?

Control Group 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

Guided Practice A researcher is studying the effect of sleep on aggression, thinking that less sleep will lead to more aggression. She has some people sleep six hours per night, some people sleep three hours per night and some people sleep as much as they want. She monitors aggressive behavior during basketball games among participants.

Guided Practice A researcher is curious to find out what the effect of classical music has on people’s level of relaxation (as measured by heart rate.) He suspects that listening to classical music will make people feel calm and more relaxed. He lets one group listen to classical music for one hour. He lets another group sit in a quiet room for one hour. After one hour, he monitors the heart rate of each participant to measure their level of relaxation.

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

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

Design Detective – Error Analysis Identify the variables (IV, DV, constants,) number of trials and control Identify the hypothesis. (If it is not stated write one for the scenario.) State at least two ways to improve the experiment

A study was conducted to determine how the number of paper clips picked up was related to the number of batteries connected to the electromagnet. The magnet connected to 1, 2, 3, 4, or 5 D Cells, was placed on the top of a pile of 100 paper clips and lifted. Identify 2 constant variables Identify the independent variable. Identify the dependent variable State the hypothesis being tested.