Southwestern University Case [PDF]

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Southwestern University Case



Discussion Questions Q1) Develop a network drawing for Hill Construction and determine the critical path. How long is the project expected to take? Expected time t = (a + 4m + b) /6 a: optimistic m: likely b: pessimistic START A -30 C-65



B-60 E-30



D-55



F – 0.1 G-30



H-20



J-10



I-30



K-0.1 L-30 FINISH



Critical Path = A-30 + C-65 + D-55 + G-30 + H-20 + I-30 + L-30 Critical Path = 260 days



Q2) What is the probability of finishing in 270 days? Project variance is summing up the variances of the critical path. V = [(b-a) / 6] ²



Variances A = 11.11



B = 69.44



D= 136.11



G = 2.78



H= 11.11



I = 44.44



L=44.44



Project Variance = 319 .43 Project Standard Deviation = √319.43 = 17.87 Probability of project completion earlier than 270 days is; Z= (due date – expected date) / project standard deviation Z = (270 – 260) / 17.87 = 0, 5596 ≈ 0.56 * Appendix I for 0.56 is 0.71226 ≈ 71% Probability of finishing in 270 days is 71% Q3) If it is necessary to crash 250 or 240 days, how would you Hill do so, and at what costs? As I note that in the case, assume that optimistic time estimates can be used a crash times. Crash Preference



Task



Crash Cost $ / day



Crash Time Optimistic



Crash Time Likely



1



A



1,500



20



30



5



C



4,000



50



65



2



D



1,900



30



55



4



G



2,500



25



30



3



H



2,000



10



20



3



I



2,000



20



30



6



L



4,500



20



30



Crash to 250 days Reducing 10 days would cost: 10 x $1,500 = $15,000 (crash down Task A) Crash to 240 days Reducing 20 days would cost: 10 x $1,900 = $ 19,000 (crash down Task D) + 10 x $1,500 = $15,000 (crash down Task A) = $34,000 TOTAL