A certified mechanic wąs timed for the repair of an automobile on 14 separate occasions. Over the same period a trainee mechanic was timed for the repair of a similar automobile. The times in minutes are given below. Certified 344 276 257 334 267 164 222 343 212 175 211 311 209 188 Trainee 222 342 178 234 398 232 377 211 309 190 351 343 177 269 a. Calculate a 99% confidence interval for the mean time taken to repair the automobile by the (i) certified mechanic and (ii) the trainee mechanic. b. Test the hypothesis that the two mean times for both mechanics are equal. Use the 5% level of significane. C. Subsequently, it was learnt that the times for the trainees were incorrectly recorded and that each of the values above is 30 minutes too small. What, if any, differences does this make to the results of the test done in part (b)?

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Do part c of the question only.
A certified mechanic was timed for the repair of an automobile on 14 separate occasions. Over
the same period a trainee mechanic was timed for the repair of a similar automobile. The
times in minutes are given below.
Certified 344
276
257
334
267
164
222
343
212
175
211
311
209
188
Trainee 222
342
178
234
398
232
377
211
309
190
351
343
177
269
a. Calculate a 99% confidence interval for the mean time taken to repair the automobile by the
(i) certified mechanic and (ii) the trainee mechanic.
b. Test the hypothesis that the two mean times for both mechanics are equal. Use the 5% level
of significane.
C. Subsequently, it was learnt that the times for the trainees were incorrectly recorded and
that each of the values above is 30 minutes too small. What, if any, differences does this make
to the results of the test done in part (b)?
Transcribed Image Text:A certified mechanic was timed for the repair of an automobile on 14 separate occasions. Over the same period a trainee mechanic was timed for the repair of a similar automobile. The times in minutes are given below. Certified 344 276 257 334 267 164 222 343 212 175 211 311 209 188 Trainee 222 342 178 234 398 232 377 211 309 190 351 343 177 269 a. Calculate a 99% confidence interval for the mean time taken to repair the automobile by the (i) certified mechanic and (ii) the trainee mechanic. b. Test the hypothesis that the two mean times for both mechanics are equal. Use the 5% level of significane. C. Subsequently, it was learnt that the times for the trainees were incorrectly recorded and that each of the values above is 30 minutes too small. What, if any, differences does this make to the results of the test done in part (b)?
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