Nyoman Rowin Sinaya, Parwadi Moengin, Bambang Endro Yuwono, Darmawan Pontan
Jurnal Indonesia Sosial Teknologi, Vol. 5, No. 6, Juny 2024 2806
Figure 1 Cost quote normal distribution graph
Normal Single Distribution
The formula for calculating the probability of winning is the same as Equation 3.
The difference with normal multi-distribution is that in a normal single distribution, the
probability of winning is calculated against the average of all competitors (Average
Bidders) or only on one bid data set, namely the lowest bid data set.
Method
Data Collection Methods
This study used primary data collection methods and secondary data. Primary data
was obtained from the construction company PT Nindya Karya, which had bidding data
in the period 2021 to 2023 on infrastructure projects with project values between IDR 100
billion and IDR 300 billion, as well as competitor bid data. Meanwhile, secondary data
are data obtained from literature sources such as course materials, websites, the internet,
scientific papers/journals, books, Electronic Procurement Services (LPSE) of the
Ministry of PUPR, and other sources that have something to do with this research.
Data Processing Method with Statistical Approach
The initial step in data processing with statistical approach methods is to determine
the method used, namely by using three methods: multi-discrete distribution method,
normal multi-distribution, and normal single distribution. The data converted into ratios
is then grouped from smallest ratio and largest ratio. After that, the mean, standard
deviation, and variance for normal multi-distribution and normal single distribution,
while discrete multi-distribution uses the initial ratio that has been analyzed, are found.
The result of this data processing is the probability of each contractor winning. In the
multi-discrete distribution method, a histogram or analysis from the Microsoft Excel
program is used, which is the same. In contrast, in the multi-normal distribution method,
a single normal distribution is used in the Z cumulative normal distribution table.
Bidding Strategy Model Data Processing Method
After finishing calculating all probability of winning using the statistical approach
of multi-discrete distribution, multi-normal distribution, and single normal distribution,
then the next step is to calculate the optimum Mark up and maximum Expected Profit
using three bid strategy models, namely the Friedman model, Gates model, and Ackoff
&; Sasieni model. After that, a comparison chart is made between the Expected Profit
against the Mark of each model.
Model Testing With Optimum Mark-Up
The optimum markup obtained from the calculation process will be tested against
the bid prices by seeing whether it will be lower (which means winning) or higher
(meaning losing) than the lowest bid price. The bid hypothesis is obtained by multiplying
the estimated cost of the contract by the markup of the calculation result and then
comparing it with the lowest bid from the winning contractor. The data used in this test
is the data of 24 project tenders used by the sample in this study, which will be tested for