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Scientific Method Notes, 9/9/14 Science is a Search for KNOWLEDGE that is based on EVIDENCE Steps of a Scientific Method 1. Gather Information. Make Observations using your 5 senses. 2. Ask questions and define the problem. Observations make us ask questions about what we experience. Science uses evidence to answer testable questions. 3. Make a Hypothesis • Observations and questions lead to possible solutions. • A hypothesis is a possible explanation that is based on observation and seeks to answer the question. • A valid hypothesis is in the form of an if, then statement 3. Hypothesis Ex: “If the gene for glowing is inserted into a plant, then the plant will produce the glowing trait.” 4. Test the hypothesis (Experiment) • A controlled test of a hypothesis is called an experiment. • A valid experiment has two variables (things that change) and a control. Variables • Any valid experiment has only two things that change - (The independent variable and dependent variable) • The independent variable is manipulated. It is the thing in the experiment that you directly change! • The dependent variable changes in response to the independent variable. It is the thing that you measure! Variables Constant Variables • Any valid experiment will only have two variables that change. All other things that could change MUST be kept the same. • Any unchanging variables are called constants or constant variables. The Control Group • One test group (the control group) is not exposed to the tested effect (variable). • Another test group is exposed to the tested effect (variable). • Keep a control group for comparison. Control and Variable • What happens when a fire fly gene (the variable) is added to tobacco genes? • This is the test plant. Quick Write! • Describe an experiment to test the effectiveness of a fertilizer on tobacco plant growth. • Define the independent and dependent variables, your control group, and three constants. 5. Analyze Data • The measurements and observations made during the experiment are called data. • Data is evidence to support the hypothesis. Data must be measurable in someway. • Data cannot be an opinion or emotion. 5. Data Cont’… • Look at data for patterns and trends. • Graphs and charts make patterns more visible. • Use the numerical data to support your conclusions! 5. Data Cont’… • 3 Types of Graphs –Line graph is your data is continuous (ie. Time) –Bar if your data comes in categories –Circle if your data is part of a whole (fractions or %’s) 5. Data Cont’… • 3 Types of Graphs –Line graph if your data is continuous (ie. Time) –Bar if your data comes in categories –Circle if your data is part of a whole (fractions or %’s) 5. Data Cont’… • Parts of a graph – – – – Title (Effect of IV on DV) Independent Variable (X-Axis) Dependent Variable (Y-Axis) Axes labeled with units 6. Form Conclusions • Conclusions are only valid if data supports it. • Reject the hypothesis if the data does not support the hypothesis. Conclusions cont’... • Error Analysis is part of conclusions. • List only KNOWN errors in the measurements • DO NOT list your guesses (e.g. “We might have....). Theory • When many hypotheses have a large body of data and support they are unified into a Theory.