Biometry Chapter 5

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1

Null hypothesis significance test

Procedures used to decide whether chance alone can account for apparent patterns in our data

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Null hypothesis

A statement embodying the idea that there is no pattern in the data or no difference between samples or no relationship between variables.

(H0)

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Research hypothesis

An educated guess at the answer to a question about cause, mechanism, or function

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Statistical hypothesis

A hypothesis that states the specific relationships between variables and therefore parallels a prediction generated by a research hypothesis.

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Statistical alternative hypothesis

The reverse statement of the statistical null hypothesis. Stating that there is a pattern, or difference or relationship between the data sets.

(H1)

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Critical significance level

This sets the decision point determining whether a null hypothesis is accepted or rejected. It is expressed as a probability. 5% is often used. (α)

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Degrees of freedom

One less than the sample size.

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Critical values

Values of statistics corresponding to a specific critical significance level and degrees of freedom. They can be looked up in a critical-value table.

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P-value / significance level

The probability of finding the observed, or more extreme, results when the null hypothesis (H0) of a study question is true.

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How do you decide to accept or reject the null hypothesis using the P-value?

Reject the null hypothesis if: P ≤ α

Accept the null hypothesis if: P > α

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Type I error

Rejecting a true null hypothesis

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Type II error

Accepting a false null hypothesis

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Power of a (statistical) test

The probability of rejecting a false null hypothesis. Or the probability of not making an error.

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Parametric test

Null hypothesis significance testing techniques for which data must meet special criteria. The data must have a normal distribution

- Use a t-Test

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Nonparametric test

Null hypothesis significance testing techniques that require fewer assumptions and do not rely on any distribution, normal or otherwise.

- Use Chi-square