Question 6.67

6.67 What’s wrong?

Here are several situations in which there is an incorrect application of the ideas presented in this section. Write a short explanation of what is wrong in each situation and why it is wrong.

  1. A manager wants to test the null hypothesis that average weekly demand is not equal to 100 units.
  2. A random sample of size 25 is taken from a population that is assumed to have a standard deviation of 9. The standard deviation of the sample mean is 9/25.
  3. A researcher tests the following null hypothesis: .

6.67

(a) The null hypothesis should contain the = sign, so the hypothesis should be “… the average weekly demand is equal to 100 units.” (b) The square root is missing; the standard deviation should be . (c) The hypotheses are always about the parameter, not the statistic, so it should be : .