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In: Statistics and Probability

A carpet company advertises that it will deliver your carpet within 15 days of purchase. A...

A carpet company advertises that it will deliver your carpet within 15 days of purchase. A sample of 49 past customers is taken. The average delivery time in the sample was 16.2 days. Assume the population standard deviation is known to be 5.6 days.

  1. State the null and alternative hypotheses.
  2. t-test or z-test?
  3. Calculate test statistic
  4. Using a critical value, test the null hypothesis at the 5% level of significance. State conclusion.

In the past the average age of employees of a large corporation has been 40 years. Recently, the company has been hiring older individuals. In order to determine whether there has been an increase in the average age of all the employees, a sample of 25 employees was selected. The average age in the sample was 45 years with a standard deviation of 5 years. Assume the distribution of the population is normal. Let a = .05.

  1. State the null and the alternative hypotheses.
  2. z-test or t-test?
  3. Test to determine whether or not the mean age of all employees is significantly more than 40 years (You may pick which method). State conclusion in a full sentence.

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