The article uncertainty estimation in railway track life- cycle cost (j. of rail and rapid transit, 2009) presented the following data on time to repair (min) a rail break in the high rail on a curved track of a certain railway line. 159 120 480 149 270 547 340 43 228 202 240 218 the sample mean and standard deviation are 249.7 and 145.1, respectively. is there compelling evidence for concluding that true average repair time exceeds 200 min? carry out a test of hypotheses using a significance level of α = 0.05.

Lian is deciding which of two gyms to join. each gym charges a monthly rate plus a one-time membership fee. lian correctly wrote and solved a system of linear equations by substitution to compare the costs of the memberships. in her work, she substituted an expression for one variable and solved for the other. this resulted in the equation 75 = 75. what can lian conclude? one gym charges $75 per month. each gym charges $75 per month both gyms charge the same monthly rate and the same membership fee. both gyms charge the same monthly rate, but not the same membership fee.