Amachine produces metal rods used in an automobile suspension system. a random sample of 15 rods is selected, and the diameter is measured. the resulting data (in millimeters) are as follows: 8.24 8.25 8.20 8.23 8.24 8.21 8.26 8.26 a.20 8.25 8.23 8.23 8.19 8.28 8.24 (a) calculate a 99% two-sided confidence interval on mean rod diameter.

Titus works at a hotel. part of his job is to keep the complimentary pitcher of water at least half full and always with ice. when he starts his shift, the water level shows 4 gallons, or 128 cups of water. as the shift progresses, he records the level of the water every 10 minutes. after 2 hours, he uses a regression calculator to compute an equation for the decrease in water. his equation is w –0.414t + 129.549, where t is the number of minutes and w is the level of water. according to the equation, after about how many minutes would the water level be less than or equal to 64 cups?