Question 9.398

13. Credit Scores in Georgia. According to CreditReport. com, the mean credit score in Georgia in 2014 was 668. A random sample of 144 Georgia residents this year shows a mean credit score of 650. Assume . Perform a hypothesis test, using level of significance , to determine if the population mean credit score in Georgia has decreased.

  1. State the hypotheses.
  2. Find the value of and the rejection rule. Also, draw a standard normal curve, indicating the critical region.
  3. Calculate . Draw a standard normal curve showing , the critical region, and .
  4. State the conclusion and the interpretation.

9.99.13

(a) –(b) −1.645; reject if (c)

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(d) Since , we reject . There is evidence that the population mean credit score in Georgia is less than 668.