1. A study was made on the post-graduation salary of a sample of 100 business graduates: the sample showed an average of $75,000 and a standard deviation of $3,000. Build a 95% and a 99% confidence interval estimator for the average salary.
An article published online claims that the average salary of business students after graduation is $80,000. What do you think of this claim, based on the observed sample?
2. A company manufactures batteries for watches. A random sample of 200 batteries is taken and the sample mean life is 5 years with a standard deviation of 0.7 years.
Construct a 90% CIE and a 99.75% CIE for the average life of the population of watches.