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Controls and Variables

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Presentation on theme: "Controls and Variables"— Presentation transcript:

1 Controls and Variables
Ana Uruena

2 What is an experiment? Testing an idea in a controlled fashion
Idea = Hypothesis Hypothesis are based on observation Change one element to affect another in a way that can be measured by the experimenter Yendor.com

3 What is a variable? Variables are the elements that change within an experiment Independent variable: element or factor the experimenter is changing in order to measure an effect on the dependent variable. There should only be one independent variable Dependent variable: the element that is measured by the scientist which is affected by the independent variable

4 What are the dependent and independent variables in this hypothesis?
The rate of osmosis is directly correlated to the size of the molecule passing through a semi-permeable membrane Water molecules Proteins Red blood cells Semi-permeable membrane Dependent variable? Rate of osmosis Independent variable? Size of the molecule passing through the membrane Adapted from Fresenius Medical Care

5 What are controls? Experimental controls are groups of test subjects that will yield a known and predictable response Eliminate experimental biased and eliminate other variables within the experiment Education.com

6 What are the different types of controls?
Negative controls: a group that is not treated with the independent variable and will give a negative response. Provides a baseline reading for your dependent variable Positive controls: a group that is treated with the independent variable and will give a known, positive response. Lets the experimenter know the experiment is working correctly, as predicted

7 What negative and positive controls could you use when testing this hypothesis?
Cholestergone, a new medication for lowering cholesterol levels Cholesteraway, the well-established medication prescribed for the past 20 years for lowering cholesterol levels Cholestergone is more effective than Cholesteraway in lowering cholesterol levels in 50 year-old African-American male patients

8 What negative and positive controls could you use when testing this hypothesis?
Cholestergone is more effective than Cholesteraway in lowering cholesterol levels in 50 year-old African-American male patients Cholestergone Cholesteraway

9 What negative and positive controls could you use when testing this hypothesis?
What can be a negative control? Patients treated with no medication or patients treated with a placebo What can be a positive control? Patients treated with Cholesteraway since it is know that this medication lowers cholesterol levels

10 QUESTIONS?

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