Determine the optimum preventative maintenance frequency for each of the pieces of equipment if breakdown time is normally distributed.
Equipment Average Time (days) Standard Deviation
A201 20 2
B400 30 3
C850 40 4
Equipment Preventative Maintenance Cost Breakdown Cost
A201 $300 $2300
B400 $200 $3500
C850 $530 $4800
Let us first find the ratio of preventive maintenance cost to sum of preventive and breakdown maintenance cost.
Preventive cost/(Preventive cost+ Breakdown cost)=300/(300+2300)= 0.1154
Now we will find the number of standard deviations from the mean represented by an area under the
Normal curve of 0.1154 (from the left tail) or alternatively, we have to find the value of Z for area of 0.3846 (0.50-0.1154=0.3846) from the mean.
If we ...
Solution determines the optimum preventative maintenance frequency for each of the pieces of equipment.