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.

Ascientist wants to use a model to present the results of his detailed scientific investigation. why would a model be useful? a )because the model makes the concepts easier to understand b) because the model is easy to put together and to use c) because the model prevents other scientists from asking questions d) because the model requires the audience to pay full attention to it i don't know what to choose because between a and d a is much more likely than d because it only wants to get the attention of the audience. i'm confuse.