Controls and Variables

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Presentation transcript:

Controls and Variables Ana Uruena

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

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

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

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

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

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

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

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

QUESTIONS?