Program 1 August 2005 1 © 2005 by Carnegie Mellon University/ODU CS 350: Assignment Kit for Program 1 Fall 2005 Version 1.1 (subject to revision)Program 1 August 2005 2 © 2005 by Carnegie Mellon University/ODU Personal Software Process for Engineers: Part I Assignment Kit for Program 1 Overview Overview This assignment kit covers the following topics. Section See Page Overview and prerequisites 2 Program 1 requirements 3 Mean and standard deviation overview 4 Using mean and standard deviation in the PSP 4 Calculating mean and standard deviation 4 A mean and standard deviation example 5 Assignment instructions 7 Guidelines and due dates 11 Grading criteria 12 Prerequisites Reading • Chapters 1 and 2Program 1 August 2005 3 © 2005 by Carnegie Mellon University/ODU Program 1 requirements Program 1 requirements Using PSP0, write a program to calculate the mean and standard deviation of a set of n real numbers. Your program can read the n real numbers from the keyboard, a file, or some other source. Use a linked list to store the n numbers for the calculations. Thoroughly test the program. At least two tests should use the data in the columns of Table 1. Expected results are provided in Table 2. In addition, you must develop at least two more test cases and provide expected output for each of your test cases. “Expected output” shows exactly what a correct program would produce for a test case. These test cases along with expected output (in the form of Table 2) are to be turned in with the program. Column 1 Column 2 Estimate Proxy Size Development Hours 160 15.0 591 69.9 114 6.5 229 22.4 230 28.4 270 65.9 128 19.4 1657 198.7 624 38.8 1503 138.2 Table 1 Test Expected Value Actual Value Mean Std. Dev Mean Std. Dev Table 1: Column 1 550.6 572.03 Table 2Program 1 August 2005 4 © 2005 by Carnegie Mellon University/ODU Mean and standard deviation Overview The mean is the average of a set of data. The average is the most common measure of location for a set of numbers. The average locates the center of the data. Standard deviation is a measure of the spread or dispersion of a set of data. The more widely the values are spread out, the larger the standard deviation. For example, say we have two separate lists of exam results from a class of 30 students; one ranges from 31% to 98%, the other from 82% to 93%. The standard deviation would be larger for the results of the first exam. Using mean and standard deviation in the PSP Mean and standard deviation are used to divide your historical size data into categories and size ranges. This will be discussed in more detail later in the semester - Estimating with PROBE II. Calculating mean and standard deviation The formula for calculating the mean is nxxniiavg∑==1 The formula for standard deviation, σ, is ()112−−=∑=nxxniavgiσ where • Σ is the symbol for summation • i is an index to the n numbers • x is the data in the set • n is the number of items in the setProgram 1 August 2005 5 © 2005 by Carnegie Mellon University/ODU A mean and standard deviation example A mean and standard deviation example In this example, we will calculate mean and standard deviation of the data in Table 3. x 186 699 132 272 291 331 199 1890 788 1601 Table 3 1. In this example, there are 10 items in the data set. Therefore, we set n = 10. 2. We can now solve the summation items in the mean formula. nxxniiavg∑==1 n x 1 186 2 699 3 132 4 272 5 291 6 331 7 199 8 1890 9 788 10 1601 Total 6389101=∑=iix 3. We can then substitute the intermediate value into the formula. 106389=avgx 9.638=avgx Continued on next pageProgram 1 August 2005 6 © 2005 by Carnegie Mellon University/ODU A mean and standard deviation example, Continued A mean and standard deviation example, cont. 4. We can now substitute avgx to calculate the intermediate values for the standard deviation formula. ()112−−=∑=nxxniavgiσ n x ()2avgixx − 1 186 205,118.41 2 699 3,612.01 3 132 256,947.61 4 272 134,615.61 5 291 121,034.41 6 331 94,802.41 7 199 193,512.01 8 1890 1,565,251.21 9 788 22,230.81 10 1601 925,636.41 Total 6389101=∑=iix()90.761,522,32101=−∑=iazvgixx 5. We can then substitute the intermediate value into the formula. 900.761,522,3=σ 878.417,391=σ 633981.625=σProgram 1 August 2005 7 © 2005 by Carnegie Mellon University/ODU Assignment instructions Assignment instructions Before starting program 1, review the top-level PSP0 process script below to ensure that you understand the “big picture” before you begin. Also, ensure that you have all of the required inputs before you begin the planning phase. PSP0 Process Script Purpose To guide the development of module-level programs Entry Criteria - Problem description - PSP0 Project Plan Summary form - Time and Defect Recording logs - Defect Type standard - Stopwatch (optional) Step Activities Description 1 Planning - Produce or obtain a requirements statement. - Estimate the required development time. - Enter the plan data in the Project Plan Summary form. - Complete the Time Recording log. 2 Development - Design the program. - Implement the design. - Compile the program, and fix and log all defects found. - Test the program, and fix and log all defects found. - Complete the Time Recording log. 3 Postmortem Complete the Project Plan Summary form with actual time, defect, and size data. Exit Criteria - A thoroughly tested program - Completed Project Plan Summary form with estimated and actual data - Completed Time and Defect Recording logs Continued on next pageProgram 1 August 2005 8 © 2005 by Carnegie Mellon University/ODU Assignment instructions, Continued Planning phase Plan program 1 following the PSP0 planning phase script. PSP0 Planning Script Purpose To guide the PSP planning process Entry Criteria - Problem description - Project Plan Summary form - Time Recording log Step Activities Description 1 Program Requirements - Produce or obtain a requirements statement for the program. - Ensure that the requirements statement is clear and unambiguous. - Resolve any questions. 2 Resource Estimate Make your best estimate of the time required to develop this program. Exit Criteria - Documented requirements statement - Completed Project Plan Summary form with estimated development time data - Completed Time Recording log