During a survey of 100 bank workers, they were asked how much time they typically provide on the work. A sample mean is equal to 8.7 hours and a standard error is equal to 0.6 hours. Construct a 95% confidence interval for a mathematical expectation. Test the hypothesis that an expected number of working hours is 9 hours.

I'm stuck on part 2.  Can you work the problem and explain how to get the answer to part B?  If it can be put into the calculator, I can't remember the process. Please explain. Thank you. Translate the statement into a confidence interval. Approximate the level of confidence.   In a survey of 1100 adults in a​ country, 68​% think teaching is one of the most important jobs in the country today. The​ survey's margin of error is ±4​%.       Question content area bottom Part 1 The confidence interval for the proportion is . 64.64,. 72.72. ​(Round to three decimal places as​ needed.) Part 2 The interval is a enter your response here​% confidence interval. ​(Round to one decimal place as​ needed.)

You measure 25 randomly selected textbooks' weights, and find they have a mean weight of 73 ounces. Assume the population standard deviation is 5.8 ounces. Based on this, construct a 95% confidence interval for the true population mean textbook weight.

Data are used either to test a hypothesis or to construct a confidence interval, but not both. Explain.