# Physical Science. What experiments have we done so far this year? Why do we do experiments? Experiments are designed & used to test a hypothesis.

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Physical Science

What experiments have we done so far this year? Why do we do experiments? Experiments are designed & used to test a hypothesis.

With the pendulum lab – we dealt with FACTORS  What are FACTORS?  parts that could change the results of the experiment if allowed  Ex: In a plant growth experiment, some factors could be:  Ex: In a student test score experiment, some factors could be:  amount of sleep the night before  time spent studying  whether or not breakfast was eaten  time of the day the test was taken

What were the factors in our pendulum lab?  Length of string  Weight on string  Push Force  Direction of swing/string slack  Where pendulum was released

That factor we CHANGED – what’s up with that?  It’s called a VARIABLE In our pendulum lab – we kept ALL the factors the same EXCEPT ONE. The term for all the factors kept the same or equal for all groups is a CONSTANT

What do we know so far? Experiment - to test questions we have - to test a hypothesis Factors ConstantVariable Can there be different kinds of Constants or Variables?

There are 2 kinds of Variables  Independent Variable (I.V.): factor that is intentionally changed  “I” change the Independent variable  This is the CAUSE of a change  Dependent Variable (D.V.): factor that changes as a result of the independent variable changing (a.k.a. Responding Variable)  responds to the other factor being changed  This is the EFFECT of the cause

The Picture so far… Experiment - to test questions we have - to test a hypothesis Factors ConstantVariable Independent Variable Dependent Variable

What Next?  The Independent variable we will change, we are going to predict what we think might happen.  If we change X, what will happen to Y?  This has a scientific term= HYPOTHESIS  a suggested solution to a problem  a prediction or an educated guess  “If”…(change in I.V.) “then”…(change in D.V.)” because of” …statement  Cause & Effect  Scope: Problem specific  addresses only one variable (independent variable)  Must be testable or measurable  statement must be helped or rejected by some type of data

The Picture so far… Experiment - to test questions we have - to test a hypothesis Factors ConstantVariable Independent Variable Dependent Variable Our hypothesis is to test the what happens to this when we change that

How do we properly design an experiment?  Only test the one VARIABLE– the variable that is the focus of your hypothesis  Keep all other factors CONSTANT  We can also do a CONTROLLED EXPERIMENT  experiment in which there are at least two groups  most experiments are controlled experiments  What experiments did we do that were controlled?

How do I know if I have a controlled experiment?  Your experiment has more than one group from which you collect data.  control group  a.k.a. “standard group”, “natural group” or “baseline group”  group(s) used for comparison – usually only one  experimental group(s)  a.k.a. “test group”  group(s) being tested – may have many test groups  What experiments did we do that were controlled?

Comparing Experimental and Control Groups Experimental GroupControl Group one factor (the Independent Variable) is changed to test the hypothesis The Independent variable is NOT changed – it is set on natural or avg separate lab set up or population that is left alone to develop naturally results compared to the control group to check if there was a response used as a comparison to see if any changes occurred in the experimental group

Adding to the Big Picture… Experiment - to test questions we have - to test a hypothesis Factors ConstantVariable Independent Variable Dependent Variable Our hypothesis is to test the what happens to this when we change that Is changed for the Experimental Group but not for the Control Group

What would you record in your data table? How Would You Organize or Arrange Your Data Table for Your Experiment?

Now that we’ve designed an experiment…  It’s time to run the experiment. Does that mean it is time to goof off?  We now need to collect DATA  observations gathered in an experiment  How?  organizing data into charts, tables, and graphs in order to draw conclusions from the data  organizing the data in a manner that allows the experimenter and others to quickly interpret the information  What data have we collected this year?

Data Table Design Column Set Up (Typical) Data Table Title: Row Set Up Data Table Title: Indep Var (units) Dep Var (Tri (Trial 1) (units) Dep Var (Trial 2) (units) Indep Var (units) Dep Var (u ) Trial 1 Dep Var (u ) Trial 2 The Data Table holds the observations of your 2 variables from your hypothesis Independent Variable with the units (LEFT column or TOP row) Dependent Variable with the units (next column or row) The Data Table needs a DESCRIPTIVE TITLE

Graph Design The Graph displays your variables in visual form (picture of your data) Independent Variable with the units on the bottom (x- axis) Dependent Variable with the units on the side (y-axis) The Graph also needs a DESCRIPTIVE TITLE Typical Graph Layout Independent Variable (units)Dependent Variable (units) Graph Title:

And also make sense of the data…Write a CONCLUSION!  an explanation of the experiment that includes describing whether or not the data supports the hypothesis and why or why not  reports and analyzes the results  must accept or reject the hypothesis  reflects on results and predicts future outcomes/tests  No experiment is a failure! You may not get the results you want, but you can still learn from it!  What conclusions have we made so far?

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