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The null hypothesis, H0,usually samples observations result purely from chance.it is the opposite of the alternate hypothesis.

Alternative hypothesis. The alternative hypothesis, denoted by H_{1} or H_{a}, is the hypothesis that the sample observations are influenced by some non-random cause.

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The National Institute of Mental Health published an article stating that in any one-year period, approximately 9.5 percent of American adults suffer from depression or a depressive illness. Suppose that in a survey of 100 people in a certain town, seven of them suffered from depression or a depressive illness. If you were conducting a hypothesis test to determine if the true proportion of people in that town suffering from depression or a depressive illness is lower than the percent in the general adult American population, what would the null and alternative hypotheses be?