Designing An Experiment

POSING A QUESTION Write the topic to be investigated in the form of a question. Word questions in a way that allows them to be answered by an investigation or an experiment. Examples of ways to begin constructing your question: What factors cause… What is the effect of… What is the relationship between… Scientific questions should be answered by scientific observations or evidence… NOT BASED ON OPINION.

DEVELOPING A HYPOTHESIS Definition: A prediction about the outcome of an experiment. A properly worded hypothesis: – i– in the form of an “IF…THEN…” statement. EX. If sugar is added to water in a vase, then the flowers will stay fresher longer. –b–based on observation and previous knowledge or experience. –m–must be something that can be tested. –c–contains the independent and the dependent variable. TESTABLE OR NOT TESTABLE EXAMPLES (T or NT) ___1. If plants are given more fertilizer, then the plants will grow taller than the plants with less fertilizer. ___2. If I get lucky then the plants will grow bigger. ___3. My plants aren’t growing bigger because I do not water them enough.

Materials: Identify and list the materials needed to conduct the experiment and revise as needed. Use bullets, not numbers. Include amounts and units (metric). Should be included in the procedures. Materials on list should match those in the procedures.

Variables Definition: factors that can change. Should be easily identified in the hypothesis and in the procedures. 3 Kinds of variables: 1. independent (Manipulated) - the factor that you purposefully change. 2. Dependent (Responding) - the factor that changes as a result of the manipulated variable. It is what you measure or observe to obtain your results. 3. Control: It is used to compare results. Constants: all factors except one that are kept the same (constant).

Plan A Procedure Describes clearly “In order” what you plan to do (step by step). Identifies the data you plan to collect Number each step. Begin with a verb – command – “Pour 50 mL of water into a beaker” A new step should begin on a new line. It is not paragraph form. Should include materials, amounts, and units. Another person should be able to conduct the same experiment by following your procedures.

Data Tables CREATING DATA TABLES A DATA TABLE is an organized arrangement of information in labeled columns & rows. DATA TABLE TIPS: · · IV is recorded in the left column & is usually ordered from smallest to largest. · · DV goes in the right column. · · UNITS must be included in column heading. · · The organization of the IV establishes a pattern of change. If there is a corresponding pattern of change in the DV, it will be easier to recognize. Ex. IV DV (w/units) (w/units) smallest May be in order if corresponding change occurs. largest If the IV & DV are properly placed in a data table, a data pair for a graph (IV,DV) can be determined from a table. Hint: (IV,DV) = (x,y) DRY MIX

Data Tables cont. Ex. MVRV (w/units) (w/units) T1 T2 T3 AVG

Data Collection CONSTRUCTING A GRAPH Graphs should include increments of equal value. This is also referred to as the scale of the graphs. To determine increment value, study the range of data collected. Using the range (lowest to highest value), decide what value each increment will receive. Common examples: 1’s, 2’s, 5’s, 10’s, 25’s, 50’s, 100’s. Identify Axes: IV = Independent (Manipulating) Variable – always written along the horizontal (x) axis. DV= Dependent (Responding) Variable – always written along the vertical (y) axis. Use the following as a checklist to determine if you have successfully completed a graph; Does my graph have a title? Are my axes labeled correctly with correct variables and units? Have I chosen an appropriate scale for my increments? Are my points plotted correctly? DV Y IV X

INTERPRETING DATA = “to find meaning in” TIPS: ~Organize data in a table & create a graph. ~Look for trends/patterns on graph. ~Make inference from data & compare to previous knowledge. ~If inference contradicts what you know, review work for errors and recheck data. DRAWING CONCLUSIONS: Definition: making a statement that sums up what you have learned. TIPS for DRAWING CONCLUSIONS: Refer back to your hypothesis. Review observations, data, graphs, trends or patterns in your results. Does your data support your hypothesis or not? Write a statement summing up what your results show. Tell if your hypothesis was correct. Back it up with data Tell what you could have done differently Drawing Conclusions