Question number 01. NOT 02 and 03

A manager at Localtel, a small telephone company, wants to determine how long service technicians need to perform a certain repair. In the past, a sample of 40 revealed that the average time to repair required 18.75 minutes, with a population standard deviation of 0.2 minutes At a 9046 confidence level, calculate the Margin of error. (1.5] b. At a 99% confidence level, calculate the Margin of error. (1.5) c As you increase the confidence level. what happens to the margin of error and why? Explain. (1.5) d. Compute the sample size of times needing to be collected to ensure they can be 90 percent confident of correctly estimating the repair time if the manager is willing to tolerate an error rate of 0.04. (3] The actual voltages of power packs labeled as 12 volts are as follows: 11,77 11.90 12 12 11 84 Calculate the 90%% confidence interval for the true variance of the voltage in the packs "Calculate the 99% upper confidence bound for the true variance of the voltage in the packs. [2] c. Interpret your findings from part (a). [1.5) The average salary for first-year teachers is $28,000 per year. Assume the distribution of yearly salary is normal with a standard deviation of $3250. What is a standard normal variable? (1] What Is the probability that a randomly selected first-year teacher earns between $21,500 and $34,5007 (3] c. Does your answer in (b) agree with the empirical rule of normal distribution? Explain