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# July+21st+slides - Hypothesis testing July 21st...

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Hypothesis testing July 21 st Corresponding to Chapter 8 in the text

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Hypothesis Testing Inferential Statistics – use data from a sample to gain information about a population - This population does not have to be real; it can be theoretical - If so, called a treatment population - Research is conducted to find out about this treatment population if it did exist
Hypothesis Testing The general goal of a hypothesis test is to rule out chance (sampling error) as a plausible explanation for the results from a research study. Hypothesis testing is a technique to help determine whether a specific treatment has an effect on the individuals in a population.

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Hypothesis Testing The hypothesis test is used to evaluate the results from a research study in which 1. A sample is selected from the population. 2. The treatment is administered to the sample. 3. After treatment, the individuals in the sample are measured.
Hypothesis Testing (cont.) If the individuals in the sample are different from the individuals in the original population, it is possible that the treatment has an effect. However, it is also possible that the difference between the sample and the population is simply sampling error

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Hypothesis Testing (cont.) The purpose of the hypothesis test is to decide between two explanations: 1. The difference between the sample and the population can be explained by sampling error (there does not appear to be a treatment effect) 2. The difference between the sample and the population is too large to be explained by sampling error (there does appear to be a treatment effect).

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Example Research question: Does supplements containing antioxidants reduce cognitive decay in elderly (>65 y.o.) population? Original population: cognitive test score u = 80, σ = 10. Treatment population: ( assume same σ ) u = ?, σ = 10.

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Step 1: State the hypotheses. The null hypothesis , H 0 , always states there is no change, no difference, no relationship in the population. Independent variable (or treatment) has no effect. The alternative hypothesis, H 1 , states there is a change, a difference, a relationship in the population. Independent variable (or treatment) has an effect.
In example The null hypothesis H 0 : In the elderly ( >65 y.o.) population, cognitive function will not be different after consuming supplement for 6 months compared to before. The alternative hypothesis, H 1 , In the elderly ( >65 y.o.) population, cognitive function will be different after consuming supplement for 6 months compared to before

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The null hypothesis _____. A. states that the treatment has no effect B. is denoted by the symbol H 1 C. is always stated in terms of sample statistics D. All of the other choices are correct.
Step 2: set the criterion for decision Determine what sample means are consistent with the null hypothesis and what sample means are inconsistent with the null hypothesis.

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