10-3-17 Parts of an Experiment cont.

Do Now: Answer the following in your science notebook Review your vocabulary words thus far and write down their definitions. Independent variable a characteristic of an experiment that determines the value of the other (dependent) variable(s). Dependent variable Dependent variable: a characteristic of an experiment that is a result of the effect or influence of an independent variable. Constant Constants: all factors in the experiment that are not allowed to change throughout the entire investigation

Groups (Experimental and Control) Independent variables should have different levels or degrees. In Kaitlin’s experiment, the different levels of the independent variable were pH of 3, pH of 7, and pH of 9. Usually, one of the levels of the independent variable is the reference point or “normal” value of the variable. The other levels will be compared with this one in order to draw conclusions from the experiment. This is called the control group. Control group: a standard of comparison for checking or verifying the results of an experiment where all variables must be held constant In Kaitlin’s experiment, the group of beans that was watered with the liquid that had a pH value of 7 would be the control group.

Groups (Experimental and Control) cont. The other levels of the independent variable are referred to as the experimental group(s). Experimental group: the group(s) being tested with the independent variable. Each experimental group should only have one factor different from each other, everything else must remain constant.

Think-Pair-Share: What were the experimental groups in Kaitlin’s experiment? Beans with the solution of pH of 3 added to them and beans with the solution of pH of 9 added to them.

Repeated Trials Repeated trials: a way to validate data by performing an investigation multiple times. Each level of the independent variable should be repeated. In general, the more times you repeat the experiment, the more valid your results are. The possibility of obtaining misleading or inaccurate results due to experimental errors will be less. Every experiment should be carried out several times and then the results of the individual trials averaged together. As a general rule, the experiment should be repeated at least 3 times. In Kaitlin’s experiment, she did not have repeated trials. She planted more than one bean in each cup but she should have planted the beans in at least 9 cups and watered three cups with each level of pH solution.

HW Review: Trade & Grade Use red ink Distance of thermometer in soil 14 possible points Type of cup Distance between cup and lamp Put an x on the incorrect term and write the correct term. Time under lamp Type of heat lamp Independent Variable: type of soil Starting temperature of containers Control Group: Potting soil Dependent Variable: Temperature of cup after heating Experimental Groups: How Dependent Variable is Measured: degrees Celsius Sand mixture of sand and soil Constants: Number of Repeated Trials: three

Student Work: Jigsaw Practice of Experimental Design Groups of 3 will be assigned to focus on 1 of 4 scenarios. Each student will be responsible for determining one of the following for each scenario: Independent variable Dependent variable Constants & repeated trials Each student performs their role individually. After 5 minutes, each student is going to get together with the other students in each group who have the same role (e.g., all the Independent variable students will get together). These are Expert Groups. In each Expert Group, you will share your ideas one by one. Then, students will return to their original group to share their answers.