Download - Chpt8 how to do an experiment
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L.O: students will review how to conduct controlled experiments.
Do now: read your
“cheat sheet”
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How to design a controlled
experiment:
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Diet pill commercials use “before and after” shots as a side by side comparison to show that the pills REALLY work!
before After!
When they ask if you want to
“supersize it”, say NO!!!!
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Scientists conduct controlled experiments as side by side comparisons too!!!!!!
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A controlled experiment ALWAYS has at least TWO groups: an experimental group and a control group.
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BOTH groups are IDENTICAL GROUPS…but
• only the experimental group gets the drug (or the treatment).
• The control groups doesn’t get the drug (or the treatment).
• Sometimes the control group is given a placebo (a fake drug or a sugar pill)
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Experimental group gets the drug or the treatment.
Control group is identical to experimental group but DOES
NOT get the drug or treatment!
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The two groups are compared to see IF the drug or treatment REALLY works!!!!!!
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a good experiment must have a large number of test subjects, be repeatable &
take place for a long time!!!!!!
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Characteristics of a good experiment:
1. Has both an experimental group and a control group.
2. Has many many test subjects.3. Is repeated many many times.4. The experiment lasts for long time (weeks, months,
years…)
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An old saying says: “A picture is worth a thousand words”….
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Scientists use graphs and tables because they make complicated data, easier to understand.
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You MUST be able to read a table and a graph!
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You MUST be able to draw a graph from a data table!
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In many experiments are looking for cause and effect relationships….
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IF one thing CAUSES something ELSE.
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Experiments have independent variables and dependent variables:
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independent variables are the cause.
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dependent variables are the effect.
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experiments are designed to see IF the independent variables causes the dependent variable to happen.
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in data tables: the independent variable is ALWAYS the first column
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in graphs: the independent variable is ALWAYS the X-axis
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in graphs: the dependent variable is ALWAYS Y-axis.
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you must be able to draw conclusions from tables and graphs.
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Now answer 1-20.
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The scientific method:
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The scientific method:
The scientific method is a method of designing an experiment.
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A well-designed experiment has the following:
• A problem: written as a question.• Materials:• A hypothesis: (a possible answer to the problem): MUST BE
WRITTEN AS AN “IF-THEN STATEMENT (NOT as a question).• The “IF” is the independent variable (the cause), the “THEN” is
the dependent variable (the effect)• Procedure: what will be done to prove or disprove the hypothesis.• Observations: the collected data.• Tables and graphs: used to display and help interpret the results.• Conclusions: was the experiment VALID , did the results support or
refute the hypothesis?
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A valid experiment is one where the data and conclusions support the hypothesis.
The hypothesis was valid (correct)!
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Now answer 21- 49
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You MUST know how to draw line graphs. There WILLLLLLLLLL definnnnnntellllly be one on the regents!!!!
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How to draw a line graph, using data from a table:
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1. Label the X-axis (ALWAYS the independent variable) label the Y-axis (ALWAYS the dependent variable)
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2. Make an appropriate scale number line for the X-axis. the units MUST be EVENLY spread out! (0,1,2,3,4 …or 0, 2,4,6,8…or 0,5, 10,
15…. Or 0, 10,20,30…or 0.0,0.5,1.0, 1.5, 2.0, 2.5….)
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3. Make an appropriate scale number line for the Y-axis. the units MUST be EVENLY spread out! (0,1,2,3,4 …or 0, 2,4,6,8…or 0,5, 10,
15…. Or 0, 10,20,30…or 0.0,0.5,1.0, 1.5, 2.0, 2.5….)
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4. Accurately plot the points.
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5. connect the points. Surround each point with a small circle,
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Now answer 50- 82.
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You probably WON’T have to draw a bar graph BUT you must know how to read them!!!!
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Example: predict how much this country’s population will grow in 2003.
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Now answer 83- 108
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Now: complete all the unfinished questions!
Make me proud!