Scien+fic Method “Truth is sought for its own sake. And those who are engaged upon the quest for anything for its own sake are not interested in other things. Finding the truth is difficult, and the road to it is rough”. Ibn alHaytham (9651039) Arab Physicist Father of the scien+fic method BIT 100: Fall 2013 1 Scien+fic Method BIT 100: Fall 2013 2 hLp://www.sciencebuddies.org/sciencefairprojects/ project_scien+fic_method.shtml Laura Ott, PhD NCSU Biotechnology Program
Transcript
Scien+fic Method
“Truth is sought for its own sake. And those who are engaged upon the quest for anything for its own sake are not interested in other things. Finding the truth is
difficult, and the road to it is rough”. Ibn al-‐Haytham (965-‐1039)
Arab Physicist Father of the scien+fic method
BIT 100: Fall 2013 1
Scien+fic Method
BIT 100: Fall 2013 2 hLp://www.sciencebuddies.org/science-‐fair-‐projects/project_scien+fic_method.shtml
Laura Ott, PhD NCSU Biotechnology Program
Scien+fic Method STEP 1: Ask ques+on – Who, what, where, when, why, how? – Ask ques+on about something you can measure.
STEP 2: Background research – Previous data – Scien+fic literature • Pubmed (www.ncbi.nlm.nih.gov/pubmed/) • Google Scholar (hLp://scholar.google.com)
BIT 100: Fall 2013 3
Scien+fic Method
BIT 100: Fall 2013 4
STEP 3: Formulate hypothesis – Educated guess as to how things will work
• If I study hard, I will get a good grade in BIT 100 – State hypothesis in a way that can be easily measured.
STEP 4: Design and execute experiment – Tests whether your experiment is true or false – Posi+ve and nega+ve controls – Reproducible • Biological replicates • Technical replicates
Laura Ott, PhD NCSU Biotechnology Program
Variables Independent variable: the variable that you have control over; it is what you manipulate or change (i.e., your test). Dependent variable: it is what you measure to see if it was affected in response to the independent variable.
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Ques+ons You are performing an experiment to test the affect of cold temperatures on bacterial cell growth. You do this by incuba+ng bacterial cultures at 20° C (cold) or 37° C (normal). You then measure bacterial cell growth by measuring cell turbidity with a spectrophotometer. 1. What is the independent variable of this experiment? 2. What is the dependent variable of this experiment?
A. 20°C temperature B. 37°C temperature C. Cell turbidity D. Bacterial cultures
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Laura Ott, PhD NCSU Biotechnology Program
Controls Posi:ve Control
• A group or treatment where the an+cipated outcome is expected (based on prior knowledge).
• Used to test experiment validity (i.e., did it work?)
Nega:ve Control • A group or treatment where no
result is expected (ofen no treatment and/or buffer-‐treated).
• Also used to test experiment validity.
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Our Experiment: We want to test if bacteria found on the sole of our shoes are resistant to the an:bio:c, ampicillin.
Nega+ve control: bacteria that has known suscep+bility to ampicillin Posi+ve control: bacteria that has known resistance to ampicillin
Replicates Technical Replicates : tests for consistency within an experiment (i.e., did we observe similar results when we ran the same sample three +mes) Biological Replicates: tests for varia+on among biologically dis+nct groups (i.e., do we see similar phenomena from mul+ple samples/subjects that are treated the same?)
Scien+fic Method STEP 5: Analyze data and draw conclusions – Compare results to controls – Determine if data supports your hypothesis • If data does not support hypothesis, need to start over at step 3 (formulate hypothesis)
Ques+ons 1. What is the first step of the scien+fic method?
A. Formulate hypothesis B. Ask a ques+on C. Background research D. Do the experiment
2. What do you do if your data does not support your hypothesis? A. Fudge data so it supports it B. Repeat experiment C. Formulate new hypothesis and design experiment(s) to test
