It is believed that more than 50% of recovering alcoholics exhibit high levels of depression. A psychological test known as the DACL was given to a random sample of 100 recovering alcoholics, and it was found that 55 had above average depression levels. Does the sample result indicate that the proportion of recovering alcoholics with above average depression levels exceeds 50%? Test the appropriate hypotheses at an alpha = 0.05 level of significance.
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For this problem, we will use a one-sided, one-sample z-test. It is a z-test because it involves proportions (as opposed to means, for which we would use a z-test or a t-test, depending on the situation). It is one-sided because we are testing that the sample proportion is above a given number as opposed to not-equal to it. It is one-sample because we are ...
The expert determines the average depression levels using hypothesis tests.