A. j. has 20 jobs that she must do in sequence, with the times required to do each of these jobs being indepen-dent random variables with mean 50 minutes and standard deviation 10 minutes. m. j. has 20 jobs that he must do in sequence, with the times required to do each of these jobs being independent random variables with mean 52 min-utes and standard deviation 15 minutes.

( a) find the probability that a. j. finishes in less than 900 minutes.
( b) find the probability that m. j. finishes in less than 900 minutes.
( c) find the probability that a. j. finishes before m. j.

Each of the following data sets has a mean of x = 10. (i) 8 9 10 11 12 (ii) 7 9 10 11 13 (iii) 7 8 10 12 13 (a) without doing any computations, order the data sets according to increasing value of standard deviations. (i), (iii), (ii) (ii), (i), (iii) (iii), (i), (ii) (iii), (ii), (i) (i), (ii), (iii) (ii), (iii), (i) (b) why do you expect the difference in standard deviations between data sets (i) and (ii) to be greater than the difference in standard deviations between data sets (ii) and (iii)? hint: consider how much the data in the respective sets differ from the mean. the data change between data sets (i) and (ii) increased the squared difference îł(x - x)2 by more than data sets (ii) and (iii). the data change between data sets (ii) and (iii) increased the squared difference îł(x - x)2 by more than data sets (i) and (ii). the data change between data sets (i) and (ii) decreased the squared difference îł(x - x)2 by more than data sets (ii) and (iii). none of the above