A researcher has noted that the repair times of a sample of 15 new lawn mowers has a standard deviation of 4 minutes. A 95% confidence interval estimate for the variance of service times for all its new lawn mowers is: a) 8.58 to 39.79
b) 1.64 to 1.96
c) 4 to 16
d) 4 to 15

In one day there are too high tides into low tides and equally spaced intervals the high tide is observed to be 6 feet above the average sea level after six hours passed a low tide occurs at 6 feet below the average sea level in this task you will model this occurrence using a trigonometric function by using x as a measurement of time assume the first high tide occurs at x=0. a. what are the independent and dependent variables? b. determine these key features of the function that models the tide: 1.amplitude 2.period 3.frequency 4.midline 5.vertical shift 6.phase shift c. create a trigonometric function that models the ocean tide for a period of 12 hours. d.what is the height of the tide after 93 hours?