Res 342 Dq1

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Discussion Question - Week One DQ 1 Explain the difference between the null hypothesis and the alternate hypothesis. How is the null hypothesis chosen? Why is it null? What is the importance of rejecting the null hypothesis in relation of the sample to the population? With a failure to reject the null hypothesis, might we make a general statement about the population based on the sample findings? The null hypothesis is always the simpler hypothesis and is generally believed to be true. It is stated in terms of "no difference" (e.g. contains an = sign). Examples of a null hypothesis are: "There is no difference in mean weight between males and females" or "Patients' outcomes are no different with or without the surgical procedure." The alternative hypothesis represents the result that the experiment would like to show. The alternative hypothesis can be stated in terms simple inequality ("Male and female weights are different"), or can be stated in terms of a result on one side or the other of the equals sign ("Females weigh less than males"). Suppose you want to design an experiment to test whether two variables are related in a certain way. What you actually do is calculate the probability, based on your data, that the variables are not related in the way you suspect. The hypothesis that the variables are not related is called the null hypothesis (null because there is no relation). When the null hypothesis is rejected at a certain probability level α (typically 0.01 or 0.05), then we are sure, with 1-α certainty, that the null hypothesis is incorrect. In other words, if we rejected the null hypothesis at α = .05, and we took 100 similar samples from the same population (choosing a different sample every time), we would expect no more than 5 of those samples to give a different statistical result. This certainly only refers to variation due to sampling error.

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