Question $3$

$[20$ marks$]$

A site engineer takes a sampling study for a gang of carpenters to study their work efficiency. The activities to be observed are divided into four categories as listed in Table $3.$ The engineer has made $74$ observations in total. The number of occurrence for each activity during the observations is also listed in this table. Assume $95\%$ confidence level $)=(1\mathrm{.}96$ is needed.

Table $3$ Observations made for the sampling study

$\backslash$table$[[$Activity categories,No$.$ of occurrence$],[$Fixing formwork $($FF$),28],[$Stripping formwork $($SF$),16],[$Cleaning formwork $($CF$),20],[$Worker Idle $($I$),10]]$

$N=\frac{Z^{2}P(100-P)}{E^2}$

$($Equation for your reference$)$

Determine the proportion of the time the workers were cleaning formwork and the degree of accuracy of the result. $[4\text{'}]$

How many additional observations need to be taken to give at least $10\%$ accuracy to all of the formwork activities, assuming $95\%$ confidence level is required $)=(1\mathrm{.}96?[11\text{'}]$

Please list any five factors that can affect construction productivity. $[5\text{'}]$