Chapter 26 practice problems

  1. True of False: If the observed significance level is 4.7%, then there is a 4.7% chance that the null hypothesis is correct.
  1. True of False: If the observed significance level is 4.7%, then there is a 4.7% chance that the alternative hypothesis is incorrect.
  1. True or False: The observed significance level depends on the data.
  1. True or False: A highly significant result could still be due to chance.
  1. True or False: If a difference is “statistically significant”, there is less than a 5% chance for the null hypothesis to be right.
  1. True or False: If Z is -1.9, then the observed value is 1.9 SE below the benchmark value for the null hypothesis.
  1. In Connecticut, the Governor’s office releases a report which states that the average salary of all teachers in the state is µ = $57,337. The teacher’s union believes this is low and that the Governor is exaggerating so that he doesn’t have to give teachers a raise this year. The teacher’s union randomly samples 100 teachers and finds that the average salary of the selected teachers is $56,000 with a SD = $7,500. Run an appropriate test of significance to determine if the teachers’ average salary is really lower, or this is just chance variation.
  1. A manufacturer of a particular digital camera with 6.0 megapixels and an optical 3X zoom lens, boasts that despite the high quality of the camera, it’s average price in retail stores is only $200. The prices (in dollars) for this particular model of digital camera are recorded for 10 randomly selected online dealers. The average price was $217.70 with a standard deviation of $17.49. Use an appropriate test of significance to determine if the manufacturer’s claim is false, or this is just due to chance variation. Assume prices are normally distributed.
  1. Two years ago, 75% of the customers of a bank said that they were satisfied with the services provided by the bank. The manager of the bank is afraid that customer satisfaction has decreased since then. She takes a random sample of 200 customers and finds that 140 are satisfied with the services provided by the bank. Run an appropriate test of significance to determine if customer satisfaction has really decreased, or if this is just chance variation.
  1. The Dean of the Business School claims that 20% of incoming freshman indicate that they will major in business or a related field. In a random sample of 400 incoming freshman, 70 indicate that they will major in business or a related field. Run an appropriate test of significance to determine if the Dean is exaggerating or if this is just chance variation.