Page 32 - Industrial Process Plant Construction Estimating and Man Hour Analysis

2 Industrial process plant construction estimating and man-hour analysis

1.2 Graphic analysis of data
A graph is a pictorial illustration of the relationship between variables. Assume
for historical man-hour data that x is the independent variable and y is the
dependent variable:

1.2.1 Straight-line graph

ð
y ¼ aþbx; Y ¼ aþ y y1Þ= x x1Þ xðÞ
ð
where
y¼dependent variable
a¼intercept value along the y-axis at x¼0
b¼slope, or the length of the rise divided by the length of the run;
b¼(y y1)/(x x1)
x¼independent or control variable