Bio-222 Class Notes
Hypotheses Notes
Science is
• Testable
• Falsifiable
• Repeatable
• Evidence-based
Hypotheses are
• Testable claims
• Statement, not question
• Uses data that can be collected from the natural world
• Should lead to specific predictions
• Must be refutable/falsifiable
•
o Hyp = hypothesis
o Conc = conclusion
o #4 = biological hypothesis
o R+N = reject the null, support biological hypothesis
o F+R+N = fail to reject the null, fail to support biological hypothesis
• Biological Hypotheses
o Reflect some underlying biological principle
• Statistical Hypotheses
o Statements that reflect features of data
o Generally mathematical equations
o Mutually exclusive
, o Comprehensive
o Tested using statistical tests that generate test statistics and p-values
o Null hypothesis (H0) is a statement of equality (=)
§ Either reject or fail to reject is statistical conclusion
§ Alpha, or p = 0.05, is the probability that H0 is true when it’s been
rejected
§ NEVER accept
§ Result informs decision about underlying biological principle in question
o Alternative hypothesis (Ha) is a statement of inequality (≠)
• The Scientific Method
o Identify the observation, problem, or question of interest
o Formulate biological and statistical hypotheses
§ Mutually exclusive and exhaustive
o Choose level of significance
§ Alpha = 0.05
o Determine appropriate test to use
o Do the experiment
o Calculate test statistic and determine p values
o Compare p values to alpha
§ Probability that we achieved these results due only to luck
§ If p < alpha then reject the null
• P is low, reject the hoe (H0)
§ If p > alpha then fail to reject the null
o State biological conclusion
§ Report conclusion with test statistic, sample size, and computer p-value
o Error
§ Type I and Type II errors
§
§ Type I is rejecting the correct H0
• Alpha is chance of making a Type I error
§ Type II is failing to reject the wrong H0
• Beta is chance of making a Type II error
, § Alpha and beta should be as small as possible
• Decreasing alpha causes beta to increase if sample size does not
change
o Decrease both by increasing n (sample size)
• Power
o The probability of rejecting the null when it is actually false (good thing)
o Use beta to determine
o Power = 1 – beta
o Power increases as sample size (n) increases
o Power decreases as number of groups (k) increases
§ Assumes a fixed sample size
o Power increases as effect size increases
§ Effect size is how big the difference is between the groups (ex for mean
comparison, how different are means)
§ Effect size (and therefore power) decreases as variability increases
o Power increases as variability deceases
o Power increases as alpha increases
Research Sources Notes
Types of Sources
• Primary Paper
o Describe certain experiments in depth, including methods
o Good for finding raw data
• Review Articles
o Takes parts of primary papers
o Good for comparing and to find other sources
• Textbooks
o Usually out of date
• Databases
o Help find primary papers
• Trade Publications
o Written more concisely for non-experts
• Websites
o Not a great source (unless CDC, etc. website)
o Written for non-experts
Lab Notebook
• What to include in general
o Background sources
o Where materials are stored
o Methods in easy to follow steps
o Goal/purpose on each page of lab notebook
o Mistakes made
, § Cross out visibly with a single line
§ Write why it was a mistake and correct it
o Changes made to procedures
o Difficulties
o Calculations
o Data and observations made
o Analyses and conclusions reached
• Make sure
o Someone can take your notebook and replicate the experiment to get similar
results
o You could look back at the notebook in 6 months and make sense of what you
wrote
o You write in pen
• Legal reasons
o Prove you were first to develop an invention
o The inventor is the one who first discovered, not the first to file for a patent
o Protects intellectual property
o Documents integrity of data for publication
• Each Page
o Objective of the day
o The date and page number
o Title of the day’s work
§ Even just brainstorming
o Thoughts, procedures, mistakes, results, calculations
o Printouts of graphs of data
o Date and initial the bottom
Importance of Citations
• Where information came from
• Acknowledges other authors’ contributions
• A trail of evidence
• Establish what is already known or thought
• Establish key players/experts in a field
• Allows replication of work
Forming CSE Citations
• Article
o Parenthetical: (Hien et al. 2016)
o End of text: Hien DFdS, Dabiré KR, Roche B, Diabaté A, Yerbanga RS, Cohuet A,
Yameogo BK, Gouagna LC, Hopkins RJ, Ouedraogo GA, et al. 2016. Plant-
mediated effects on mosquito capacity to transmit human malaria. PLoS Pathog.
12: 1-17. https://doi.org/10.1371/journal.ppat.1005773
§ Ignore hyphens in last names
Hypotheses Notes
Science is
• Testable
• Falsifiable
• Repeatable
• Evidence-based
Hypotheses are
• Testable claims
• Statement, not question
• Uses data that can be collected from the natural world
• Should lead to specific predictions
• Must be refutable/falsifiable
•
o Hyp = hypothesis
o Conc = conclusion
o #4 = biological hypothesis
o R+N = reject the null, support biological hypothesis
o F+R+N = fail to reject the null, fail to support biological hypothesis
• Biological Hypotheses
o Reflect some underlying biological principle
• Statistical Hypotheses
o Statements that reflect features of data
o Generally mathematical equations
o Mutually exclusive
, o Comprehensive
o Tested using statistical tests that generate test statistics and p-values
o Null hypothesis (H0) is a statement of equality (=)
§ Either reject or fail to reject is statistical conclusion
§ Alpha, or p = 0.05, is the probability that H0 is true when it’s been
rejected
§ NEVER accept
§ Result informs decision about underlying biological principle in question
o Alternative hypothesis (Ha) is a statement of inequality (≠)
• The Scientific Method
o Identify the observation, problem, or question of interest
o Formulate biological and statistical hypotheses
§ Mutually exclusive and exhaustive
o Choose level of significance
§ Alpha = 0.05
o Determine appropriate test to use
o Do the experiment
o Calculate test statistic and determine p values
o Compare p values to alpha
§ Probability that we achieved these results due only to luck
§ If p < alpha then reject the null
• P is low, reject the hoe (H0)
§ If p > alpha then fail to reject the null
o State biological conclusion
§ Report conclusion with test statistic, sample size, and computer p-value
o Error
§ Type I and Type II errors
§
§ Type I is rejecting the correct H0
• Alpha is chance of making a Type I error
§ Type II is failing to reject the wrong H0
• Beta is chance of making a Type II error
, § Alpha and beta should be as small as possible
• Decreasing alpha causes beta to increase if sample size does not
change
o Decrease both by increasing n (sample size)
• Power
o The probability of rejecting the null when it is actually false (good thing)
o Use beta to determine
o Power = 1 – beta
o Power increases as sample size (n) increases
o Power decreases as number of groups (k) increases
§ Assumes a fixed sample size
o Power increases as effect size increases
§ Effect size is how big the difference is between the groups (ex for mean
comparison, how different are means)
§ Effect size (and therefore power) decreases as variability increases
o Power increases as variability deceases
o Power increases as alpha increases
Research Sources Notes
Types of Sources
• Primary Paper
o Describe certain experiments in depth, including methods
o Good for finding raw data
• Review Articles
o Takes parts of primary papers
o Good for comparing and to find other sources
• Textbooks
o Usually out of date
• Databases
o Help find primary papers
• Trade Publications
o Written more concisely for non-experts
• Websites
o Not a great source (unless CDC, etc. website)
o Written for non-experts
Lab Notebook
• What to include in general
o Background sources
o Where materials are stored
o Methods in easy to follow steps
o Goal/purpose on each page of lab notebook
o Mistakes made
, § Cross out visibly with a single line
§ Write why it was a mistake and correct it
o Changes made to procedures
o Difficulties
o Calculations
o Data and observations made
o Analyses and conclusions reached
• Make sure
o Someone can take your notebook and replicate the experiment to get similar
results
o You could look back at the notebook in 6 months and make sense of what you
wrote
o You write in pen
• Legal reasons
o Prove you were first to develop an invention
o The inventor is the one who first discovered, not the first to file for a patent
o Protects intellectual property
o Documents integrity of data for publication
• Each Page
o Objective of the day
o The date and page number
o Title of the day’s work
§ Even just brainstorming
o Thoughts, procedures, mistakes, results, calculations
o Printouts of graphs of data
o Date and initial the bottom
Importance of Citations
• Where information came from
• Acknowledges other authors’ contributions
• A trail of evidence
• Establish what is already known or thought
• Establish key players/experts in a field
• Allows replication of work
Forming CSE Citations
• Article
o Parenthetical: (Hien et al. 2016)
o End of text: Hien DFdS, Dabiré KR, Roche B, Diabaté A, Yerbanga RS, Cohuet A,
Yameogo BK, Gouagna LC, Hopkins RJ, Ouedraogo GA, et al. 2016. Plant-
mediated effects on mosquito capacity to transmit human malaria. PLoS Pathog.
12: 1-17. https://doi.org/10.1371/journal.ppat.1005773
§ Ignore hyphens in last names
