3. (12 points) A personnel officer in a governmental agency administered four newly developed aptitude test to each of 25 applicants for entry level clerical positions in the agency. For purpose of the study, all 25 applicants were accepted for positions irrespective of their test scores. After a probationary period each applicant was rated for proficiency on the job. The scores on the four tests X1, X2, X3, X4 and the job proficiency score is Y for 25 applicants was collected. Based on the added value plot recommend which tests score may be dropped and why? Also indicate if any variable should be included in the model in certain form (eg. Linear, quadratic or cubic etc.) Figure 1 Added variable plot 5 04 024 O 210 190 021 0 019 0226 00 -5 O 0 % o X1 | others 024 -40 -20 O 21 o O 00 O 0 O O 5 10 -20 -10 0 10 X2 others 70 019 240 021 o 00 240 226 0 O 0 20 -6 -4 -2 0 2 4 6 X3 | others X4 others