Suppose a population unkown population mean and population standard deviation 2.5. A sample of 450 observations has a sample mean of ˉx=62. Find a 95% confidence interval.
What are the z-scores corresponding to a 70% confidence level?
Suppose average pizza delivery times are normally distributed with an unknown population mean and a population standard deviation of six minutes. A random sample of 28 pizza delivery restaurants is taken and has a sample mean delivery time of 36 minutes. Find a 90% confidence interval for the population mean delivery time.
From a population with population mean 16 and standard deviation 2 a sample of 35 observations is taken. Provide an interval such that there is an 80 chance that the sample mean falls within the range.
Suppose scores on exams in statistics are normally distributed with an unknown population mean and a population standard deviation of 3 points. A random sample of 36 scores is taken with an mean score of 72. Find a 98% confidence interval for the mean exam score of the population.