Scientific Method and Experimental DesignPresentation Transcript
Scientific Method and Experimental Design
Goal of Science Steps of Scientific Method Hypothesis Independent and Dependent Variable Experimental Design Sample Size and Validity Data Collection and Organization Conclusions The Characteristics of Science
Science A process, based on observations and experimentation, that provides explanations of natural events or problems Uses the scientific method Conclusions rely on data and facts, inferences and observations
Steps of the Scientific Method
Collect and analyze data
An possible explanation of a natural event or observation that can be tested by additional observations or experimentation Must be testable! Written as “If……., then……” statement Hypothesis
Identify 2 crucial variables to write hypothesis
Independent variable : The factor that is deliberately manipulated in an experiment (also called experimental variable)
“ Presumed cause”
Dependent variable : The variable that changes in response to changes in the independent variable. It is what is measured in the experiment
“ Presumed effect or result”
Hypothesis is written as follows:
If independent variable , then dependent variable
Ex. If 100 grams of fertilizer is applied to a lawn, then the lawn will grow at a faster rate.
IV amount of fertilizer
DV rate of growth
Controlled Experiments Tests one variable at a time (experimental variable) Controlled experiments include 2 groups: Experimental Group Exposed to experimental variable Control Group Not exposed to experimental variable, all variables held constant All extraneous variables must be held constant in both groups!
Sample Size (N)
The number of subjects involved in experimentation
Decreases impact of chance events and error
Increase reliability of results (validity)
The extent to which experimental results can be generalized to other settings or situations To increase validity, increase N Ex. 7 tanks, 6 experimental and 1 control Each tank has 100 single celled green organisms All variables held constant except the light Validity
Quantitative Data: numerical data Ex. Measurement of depth in inches Qualitative Data: descriptive data collect with your senses Ex. Color Use data tables and charts to more effectively display data for analysis Record and Analyze Data
Conclusion Refers back to the hypothesis “ Supported” or “rejected” Use data to support If the same conclusions are supported over a long enough period of time they become theories
Scientific Theories Explanation for a natural event Based on observation, experimentation, inference, and evidence Explains current observations and predicts future events
The Characteristics of Science
Based on the assumption that the natural world can be investigated and explained in terms we can understand.
Based on the results of controlled experimentation and observations.
The results must be repeatable and verifiable.
Must be refutable. If a hypothesis is not supported by evidence it must be rejected or re-worded