A manager of an e-commerce company would like to determineaverage delivery time of the products. A sample of 25 customers istaken. The average delivery time in the sample was four days with astandard deviation of 1.2 days. Suppose the delivery times arenormally distributed.
- Provide a 95 % confidence interval for the mean deliverytime.
- The manager claims that the average delivery time of theirproducts does not exceed 3 days. Write the null and alternativehypothesis regarding to the claim of  the manager.
- Test the manager’s claim at 95 % confidence level.
For an effective parental skill study, a researcher asked: Howmany hours do your kids watch the television during a typical weekin Barcelona? The mean of 100 Kids (ages 6-11) spend about 28 hoursa week in front of the TV. Suppose the study follows a normaldistribution with standard deviation 5.
- Estimate the mean of all kids (ages 6-11) in Barcelona, using99% confidence interval. (show all the calculations)
- Write the conclusion of your result
