### How large a sample must we take in order to be confident

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if standard deviation of the lifetimes of television tubes is estimated as 100 hours,how large a sample must we take in order to be a) 95% b) 90% c) 99 d) 99.73% confident that the error in the estimated mean lifetime will not exceed 20 hours.

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 Find that the average man in our sample weighs 180 pounds : Suppose we want to estimate the average weight of adult males in greater metropolitan Atlanta area. We draw a random sample of 1,000 men from a population of 1,000,000 men and weigh them. Calculate value of cohesion and angle of internal friction : A cylindrical soil sample fails under an axial vertical stress of 160 kN/m^2, when it is laterally unconfined. The failure plane makes an angle of 50 degrees with the horizontal. Evaluate the mole fraction and partial pressure of each gas : Calculate the mole fraction and partial pressure of each gas, and the total pressure in the tank. a) Boron trifluoride - mole ratio - partial pressure b) Sulfur hexafluoride -mole ratio -partial pressure Heat and humidity in an underground mining situation : List the main sources of heat and humidity in mines and briefly describe the methods that can be used to control heat and humidity in an underground mining situation. How large a sample must we take in order to be confident : how large a sample must we take in order to be a) 95% b) 90% c) 99 d) 99.73% confident that the error in the estimated mean lifetime will not exceed 20 hours. Find probability that sample standard deviation will exceed : it is found that the lifetimes of television tubes manufactured by a company have a normal distribution with mean of 2000 hours and standard deviation of 60 hours. if 10 tubes are selected at random Determine what is the displacement from t : Suppose that the acceleration of the train during the interval time from t=2 to t=4 s is a 2t m/s^2, and at t = 2 s its velocity is v = 180 km/hr. What is the train's velocity at t = 4 s What is the impedance of the circuit at resonance : A series RLC circuit has R = 75 %u03A9, L= 20 mH, and a resonance frequency of 4.0 kHz. What is the impedance of the circuit at resonance Design speed station of pc station of pt deflection angle : A horizontal Curve is designed for a two lane mountainous terrain. The following data are known. intersection angle: 40 degrees tangent length: 436.76 ft Station on PI: 2700+10.65 fs=0.12 e=0.08

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