The time in hours for a worker to repair an electrical

Reference no: EM13628309

The time in hours for a worker to repair an electrical instrument is a Normally distributed random variable with a mean of ? and a standard deviation of 50. The repair times for 12 such instruments chosen at random are as follows:

183

222

303

262

178

232

268

201

244

183

201

140

Part a) Find a 95% confidence interval for ?. For both sides of the bound, leave your answer with 1 decimal place. ( , ).

Part b) Find the least number of repair times needed to be sampled in order to reduce the width of the confidence interval to below 26 hours.

Reference no: EM13628309

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