COMPUTER GRADED CONSTRUCTION ESTIMATING EXERCISES - AN EXAMPLE –

INTRODUCTION

A series of estimating exercises is used in building construction estimating classes. Each exercise is designed to require quantity take off for the items specified in a particular division of the specifica­tions. Exercises have been developed for Division 3 - Concrete and Division 4 - Masonry. All students are assigned the same exercise, but each student has a different set of variables and parameters. This was done to encourage individual student effort without using a different exercise for each student. Since each student has the same exercise there is also the same level of difficulty. Students can compare their methods for arriving at the desired quantities, but not the final answers since they are not the same. Following is a detailed description of one of these exercises, Assignment A-3, and how it was administered in the classroom.

DEVELOPMENT OF STUDENT ASSIGNMENT

Assignment A-3, a poured in place concrete control building, has been used for several semesters. It requires a quantity take off for items in Division 3 - Concrete. In the past, dimensions were changed every semester to prevent students from referring to previous students' work. This did not,. however, prevent students from comparing answers with each other. It was difficult to determine which students did their own work. Some students were tempted to copy another's answers or work.

The first step in adapting this exercise for computer grading was to revise the drawings. Selected dimensions and parame­ters for Assignment A-3 were defined using variables A, B, C, D, E, F, G, and H (See Figure 2). These letters are the student variables. A set of distinctly different values for these variables was prepared for each student and identified with a player number. For example:

PLAYER 1, A=22, B=20, C=18, D=8, E=9, F=24, G=12, H=16.

PLAYER 2, A=23, B=22, C=18, D=9, E=9, F=18, G=16, H=12.

It can be seen from the drawings that chang­ing these variables results in different quantities required for concrete, rebar and other work items. Good design and construction practice were used in selecting the values for these variables in order to achieve realistic conditions.

The second step was to prepare a student handout consisting of general information and notes (See Figure 1), the revised drawing (See Figure 2), and a formatted answer sheet (See Figure 3). The general information sheet contains instructions to the student on the scope of work and provides additional information not shown on the drawings. The drawings show a floor plan, building section, and details. Also shown on the drawings are the variables. The answer sheet lists the work items to be taken off with units of measure for each item.

In step three a basic program was written to compute the quantities for all work items using the appropriate student variables for each player number. The computed answers are then compared to the keyed in student answers. The work items, student answers, and scoring are recorded on a printout.

CLASSROOM PROCEDURE

All students are given a copy of the Assignment A-3 handout. Each student is assigned a player number and given the corresponding list of values for the student variables. The instructor discusses and explains the scope of the assignment. Any problems or questions are resolved.

Each student computes answers for the required items on the answer sheet using his assigned values for the variables. Typically students are allowed two class periods to make their calculations. The student then enters his answers on his answer sheet. The answer sheet is formatted to correspond to the input prompts which appear on the computer screen. This allows the student to input his answers without having to spend a lot of time searching for each one.

The instructor loads the program for Assignment A-3 into an IBM PC. Each student enters his answers into the computer responding to prompts on the screen. First he inputs his name and player number (See Figure 4). This player number tells the computer which set of values to use for the variables in its computations.

Next the student enters his answers from his- answer sheet for each work item following the prompts on the screen (See Figures 5 and 6).

After all of a student's answers are entered, the computer calculates the correct answer for each work item, compares them to the student's answers, and prints the results. Incorrect answers are marked "WRONG" on the printout (See Figure 7).

Students with wrong answers are required to recalculate those answers, revise their answer sheets, and try again. This process is repeated until all answers are correct. Each time the student makes another "RUN" it is recorded by a counter built into the program. The number of "RUNS" each student makes is shown on their printout.

GRADING

The program for assignment A-3 is designed to accept as correct student answers within five percent of the computed answer for most work items. This five percent tolerance has been adjusted for work items with a low numerical value. Other tolerances may be used when appropriate. Student answers which exceed these tolerances are marked "WRONG". Grading is based on the number of "WRONG" answers and on the number of computer "RUNS" required for the student to get all answers correct. At the instructors option he can printout school solutions, student answers and grading. This allows for a comparison of the student's answers with the correctly computed answers. This option is not available to the students (See Figure 8).

CLASSROOM RESULTS

Assignment A-3 was one of several computer graded exercises used in two sections of construction estimating classes in the Fall of 1986. The use of these computer graded exercises resulted in a change in student attitude. Since the students were not in a position to compare answers, each was motivated to do his own work. The students discussed among themselves methods for arriving at their answers. This promoted the learning process, as did having to recalculate wrong answers. A competitive atmosphere developed among the students as to who could finish first. These computer graded exercises also required additional hands on computer use for students. The formatted answer sheet and screen prompts contributed to logical structured estimates. This structuring helped the students learn how to attack their future projects when they no longer had formatted answer sheets to guide them.

FACULTY BENEFITS

These computer graded exercises allow the instructor to be more objective in determining student grades. Each student has a specific number of "WRONG" answers and computer "RUNS" which provides guidelines for grading. Much less time was spent by the instructor in the tedious task of checking each student's calculations. The instructor could also feel more confident that each student was being graded on their own individual work. He no longer had to guess how much group effort was represented on a student's printout. Grading errors were also reduced.

CONCLUSIONS

REFERENCES:

None. All work is original.