An operation assembling PCs receives components from its suppliers and assembles their products according to customer demand. Although there are many different combinations of components, and although the components are always changing as new updated versions are supplied, the company wants to establish work times so that it can plan its staff requirements in the future. The assembly task has four elements, collecting components from the store, assembling the components, running the standard tests and rectifying if necessary, and finally packing and despatching the PC. Table 9.7 shows the mean and standard deviation of the basic times for each element of the assembly task. These data were derived from hundreds of direct observations. (a) What assembly time would you recommend is used for planning purposes? (Use Table 9.6 to calculate allowances.) (b) Is there any other advice that you would want to give the company and are there any assumptions that you would want to check out?

Table 9.7 The mean and standard deviation of the basic times for each element of the assembly task Element of assembly task Mean time (minutes) Collect components Assemble PC Test and rectify Pack and despatch 14.6 28.7 18.3 5.4 Standard deviation of time (minutes) 1.2 2.7 6.8 1.2