Lecture6-note

Lecture6-note - The project A simple study of pine tree...

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1 Bio7 project A statistical study of pine tree needles at UCI Copyright Brigitte Baldi 2006 © The project A simple study of pine tree needles. Learning objectives: ± Conduct your own field biology project, from beginning to end ± Apply what you learn in class concretely ± Apply more than one topic learned in class to a single problem. Your project report is due the last of week in class. It should contain graphs + about 1-2 pages of text & equations ( as a guideline ). Observational study ± 2 species required ± Pine needles length Î Is there a difference in mean needle length between the 2 species? Pine trees, cones, and needles Cones Needles Phase 1: Study design & data collection ± Preliminary study: Explore the factors influencing your response variable in nature ± Walk around and observe different pine trees ± Gather a few needles from different parts of a tree ± Then sit down and think… ± Define your data collection procedure ± How many needles, from how many trees, where? ± Think about why you make those choices ± How will you ensure the randomness of your samples? ± Collect data ± Choose an appropriate sample size ( discussed after midterm ) ± Be careful to keep the needles in well labeled containers Questions ± Why would you need to gather more than one needle for each species? ± What kind of variability do you see when taking a tour of campus? ± What do you think affects pine needle length? ± What can you do to average out the effect of confounding variables? ± How do you plan on designing your study? What will you control for?
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2 Design Number of trees? Trees chosen how? Number of branches? Branches chosen how? Number of needles? Needles chosen how? Species A sample design (same design for species B) Method used to get an SRS Decide on your study design. Æ How many trees, how many branches, how many locations … ? Æ Which choices will be random and which ones will be systematic? Æ What will you do to make sure each sample is a Simple Random Sample? Make a diagram of these choices (look back at chapters 8-9). ± As with any study / experiment, always always plot your raw data first. Æ What type of graph? ± Make a graphical summary that can help you describe your sample distributions. Æ What type of graph? ± Look for unexpected trends or values. If any, try to find out why. ± Choose an appropriate numerical summary for a comparative graph. Phase 2: Exploratory data analysis ± Define your hypotheses and select the corresponding statistical test ± Summarize the whole picture, taking everything into account ± Conclude __________________ Don’t hesitate to seek help and ask questions ± Office hours, email, after class ± All necessary information on the website (Project page) ± We’ll discuss this project again as we progress through the class Phase 3: Statistical tests / conclusions Scatterplots ± After plotting two variables on a scatterplot, we describe the relationship by examining the form , direction , and strength of the association. We look for an overall pattern … ±
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This note was uploaded on 04/26/2008 for the course BIOL 7 taught by Professor Luo during the Fall '07 term at UC Irvine.

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Lecture6-note - The project A simple study of pine tree...

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