# Shared Flashcard Set

## Details

Biometry part 2
Exam 2
30
Mathematics
10/13/2013

Term
 Hypothesis testing is an extension of what?
Definition
 Estimation
Term
 Define a hypothesis
Definition
 A statement (prediction) about one or more populations.
Term
 What is the difference between research and statistical hypotheses?
Definition
 Research - the conjecture that motivates the research (these lead to stat. hyp.)Statistical - are stated in such a way that they may be evaluated by appropriate statistical techniques
Term
 Describe "the whole process" for research
Definition
 1.State the biological problem and define your population of interest2.Decide on what kind of data, treatments, methods, assumptions, etc. are necessary3.Formulate a protocol4.Perform a Pilot Study5.Collect Data6.Analyze the Data7.Interpret the Results
Term
 Our hypothesis comes in a set of what two hypotheses?
Definition
 Null Hypothesis and Alt hypothesis **Hyp are always based on pop parameters, not sample stats**
Term
 Hypotheses can be formulated to test for what 3 patterns?
Definition
 An effect in either direction (not equal)An effect in one direction (< or >)A directional effect of a certain minimum size (A-B=2)
Term
 What is a type 1 error?
Definition
 rejecting Ho when it is true
Term
 What is a type 2 error
Definition
 accepting Ho when it is untrue
Term
 What does a non-directional hypothesis specify?
Definition
 That only an effect exists (the p-value is expected to be different)
Term
 What does a directional hypothesis specify?
Definition
 The value of one group is expected to be greater than another group
Term
 Is a directional or non-directional hypothesis more powerful?
Definition
 A directional hypothesis is more powerful, but if there is a difference in the direction not specified, the difference won't be found
Term
 Define "significantly different"
Definition
 More different than we would expect simply due to random chance (he says we must specify this carefully)
Term
 What happens to stat sig as N increases?
Definition
 We expect less variation due to chance
Term
 Absence of evidence is not evidence of absence
Definition
 That is all. I don't know how to put that in a question.
Term
 We can only make statistical claims regarding which hypothesis?
Definition
 The null one (fail to reject Ho and reject Ho) his example was the judicial system
Term
 What are α and β ?
Definition
 α = Pr(Type I Error) = Pr(false positive)β = Pr(Type II Error) = Pr(false negative)Classical hypothesis testing controls α and β is decided afterward – ‘Post-hoc’These values are inversely proportional, but as N increases, both a and B decrease
Term
 What is power?
Definition
 Power = 1 – βAnd power is the prob of rejecting the Ho given that the Ho is actually false
Term
 Describe the biological assumptions for a statistical test
Definition
 1) all observations are random and unbiased2) all obs are random3)All samples are representative of the population4) The populations are normally distr5) pops are identical in all characteristics aside from the mean
Term
 Which statistical test do you use for mean? Median?
Definition
 t statistic; Mann-Whitney U statistic
Term
 What happens to the t distribution as you increase df?
Definition
 The curve becomes more narrow and tall.
Term
 What does your p value mean?
Definition
 The probability of obtaining a test-statistic value as extreme or more extreme than the observed value from the data, assuming the null hypothesis is true.
Term
 What is the posterior power of a test?
Definition
 Symbolized by beta, it is the inverse of p-value and indicates the power of a test.
Term
 When do you fail to reject Ho?
Definition
 When p value is greater than a
Term
 What kind of hypothesis test do you run on non-independent samples?
Definition
 Paired comparison test
Term
 Name 3 methods of pairing data for paired comparison test
Definition
 - same experimental unit before and after treatment-littermates of same sex randomly assigned to 2 treatments- matching experimental units based on characteristic related to the measure of interest (weight, blood pressure)
Term
Definition
 - lots of time and expense finding pairs- loss of df (would have been 2n-2, now it's n-1)
Term
 What is ANOVA?
Definition
 is a statistical technique where the total variation present in a set of data is partitioned into 2 or more components. You can determine the magnitude of different class variables contributing to the toal variation.
Term
 What are the 2 purposes of ANOVA?
Definition
 (1) Estimate and test hypotheses about population variances(2) Estimate and test hypotheses about population means (we’ll focus mostly on this)
Term
 What are 2 sources of variation?
Definition
 Total variation = model variation + residual variation
Term
 What are the assumptions of ANOVA?
Definition
 1. Normal distribution2. Independence of errors (obs are not infl by each other)3. Homoscedasticity (homogeneity of variances)
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