Managerial Decision Making and Problem Solving Computer Lab Notes 1

2 Basic Excel functions and operators Arithmetic Operations – Addition of cells A1and B1: – Subtracting cell B1 from A1: – Multiplication of cell A1 by B1: – Division of cell A1 by B1: – Cell A1xraised to the power in cell B1: = A1 + B1 = A1 - B1 = A1 * B1 = A1 / B1 = A1^ B1

3 Relative and absolute addresses – All row and column references are considered relative unless preceded by a “$” sign – When copied, ‘relative addresses’ change relative to the original cell position. Example: Cell E5 Cell G9 = A1+B$3+$C4+$D$6 = C5+D$3+$C8+$D$6 Basic Excel functions and operators

4 Arithmetic functions – Sum=SUM(A1:A3) Returns the sum A1+A2+A3 – Average=Average(A1:A3) Returns the arithmetic average of cells A1, A2, A3 – SUMPRODUCT=SUMPRODUCT(A1:A3,B1:B3) Returns the sum of products A1  B1+A2  B2+A3  B3 – ABS=ABS(A3) Returns the absolute value of the entry in cell A3. Basic Excel functions and operators

5 Arithmetic functions – continued – SQRT=SQRT(A3) Returns  A3 – MAX=MAX(A1:A9) Returns the Maximum of the entries in cells A1 through A9. – MIN=MIN(A1:A9) Returns the Minimum of the entries in cells A1 through A9. Basic Excel functions and operators

6 Statistical functions – RAND()=RAND() Generate a random number between 0 and 1 from a uniform distribution. – Probabilities and variable values under the normal distribution NORMDISTNORMINV =NORMDIST(25,20,3,TRUE)=NORMINV(.55,20,3) Returns P(X<25) when  = 20Returns x 0,, such that P(X<x 0 )=.55 and  = 3 when  = 20 and  = 3 NORMSDISTNORMSMINV =NORMSDIST(1.78)=NORMSINV(.55) Returns P(Z<1.78)Returns z 0, such that P(Z<z 0 )=.55 Basic Excel functions and operators

7 Statistical functions – Probabilities and variable values under the t- distribution TDISTTINV =TDIST(1.5,12,1)=TINV(.05,15) Returns P(t>1.5) when =12Returns t 0,, such that P(t t 0 )=.025 when =15. Note: =TDIST(1.5,12,2) returns P(t 1.5) when =12. Basic Excel functions and operators

8 Statistical functions – Other probability distributions – Poisson=POISSON(7,5,TRUE) Returns P(X<7) for Poisson with = 5. Note: false returns the probability density P(X = 7) – EXPONDIST=EXPONDIST(40,1/20,TRUE) Returns P(X<40) for the exponential distribution with 1/  =20 Note: false returns the probability density f(40)=20exp(-20(40)) Basic Excel functions and operators

9 Conditional functions: – IF=IF(A4>4,B1+B2, B1 – B2) Returns B1+B2 if A4>4, and B1 – B2 if A4  – SUMIF=SUMIF(F1:F12, “>60”,G1:G12) Returns G1+G2+…+G12 only if F1+F2+…+F12>60 Basic Excel functions and operators

10 – VLOOKUP=VLOOKUP(6.6,A1:E6,4) If the values in column A of a given table [A1:E6] are sorted (in an ascending order), VLOOKUP finds the largest value in column A that is less than or equal to 6.6, identifies the row it belongs to, and returns the value in the fourth column that correspond to this row. Note: If the values in column A are not sorted, =VLOOKUP(6.6,A1:E6,4,FALSE) finds the value 6.6 in column A, identifies the row it belongs to, and returns the value in the fourth column that corresponds to this row. Basic Excel functions and operators

Using Excel Solver to Find an Optimal Solution and Analyze Results 11

Using Excel Solver to Find an Optimal Solution and Analyze Results 12

Using Excel Solver to Find an Optimal Solution and Analyze Results 13

Using Excel Solver to Find an Optimal Solution and Analyze Results 14

Using Excel Solver to Find an Optimal Solution and Analyze Results 15

16 Using Excel Solver – Optimal Solution

17 Using Excel Solver –Answer Report

18 Using Excel Solver –Sensitivity Report

19 Solver – Infeasible Model

20 Solver – Unbounded solution

21 Solver does not alert the user to the existence of alternate optimal solutions. Many times alternate optimal solutions exist when the allowable increase or allowable decrease is equal to zero. In these cases, we can find alternate optimal solutions using Solver by the following procedure: Solver – An Alternate Optimal Solution

22 Observe that for some variable X j the Allowable increase = 0, or Allowable decrease = 0. Add a constraint of the form: Objective function = Current optimal value. If Allowable increase = 0, change the objective to Maximize X j If Allowable decrease = 0, change the objective to Minimize X j Solver – An Alternate Optimal Solution