Cost estimating relationships (CERs) are sometimes used to estimate the cost of a project by comparing it to similar past projects. Six different CERs were applied to six different engineering projects to project their costs. After the projects were completed, their true cost was compared to the projected cost. The table below shows the percent error between the projected and actual costs.

	Project
CER	1	2	3	4	5	6
1	1244	21	82	2221	905	839
2	281	129	396	1306	336	910
3	220	84	458	543	300	794
4	225	83	425	552	291	826
5	19	11	-34	121	15	103
6	-20	35	-53	170	104	199

a) Do the CERs differ in their ability to accurately estimate cost?

b) Which, if any, CERs differ from the others?

c) Which CER would you recommend for your next project?