A certified technician was timed for the repair of a washing machine on 14 separate occasions. Over the same period a trainee technician was timed for the repair of a similar washing machine. The times in minutes are given below Certified 340 276 257 334 267 164 222 343 212 175 211 351 209 188 Trainee 222 342 180 340 398 232 377 211 319 190 351 243 177 269 a. Calculate a 95% confidence interval for the mean time taken to repair the washing machine by the (i) certified techician and (ii) the trainee technician. b. Test the hypothesis that the difference between the two mean times for both technicians is 15 minutes. Use the 5% level of significance. c. Subsequently, it was learnt that the times for the certified technician were incorrecly recorded and that each of the values above is 20 minutes too small. What, if any, difference does this make to the results of the test done in part (b)?
A certified technician was timed for the repair of a washing machine on 14 separate occasions.
Over the same period a trainee technician was timed for the repair of a similar washing machine.
The times in minutes are given below
Certified 340 276 257 334 267 164 222 343 212 175 211 351 209 188
Trainee 222 342 180 340 398 232 377 211 319 190 351 243 177 269
a. Calculate a 95% confidence interval for the mean time taken to repair the washing
machine by the (i) certified techician and (ii) the trainee technician.
b. Test the hypothesis that the difference between the two mean times for both
technicians is 15 minutes. Use the 5% level of significance.
c. Subsequently, it was learnt that the times for the certified technician were incorrecly
recorded and that each of the values above is 20 minutes too small. What, if any,
difference does this make to the results of the test done in part (b)?
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