The table below contain the results of an experiment involving fifteen programmers randomly assigned to implement an algorithm in a specified programming language. The outcome variable is the number of lines of code.
| Group 1 Language X |
Group 2 Language Y |
Group 3 Language Z |
|---|---|---|
| 144 | 101 | 130 |
| 120 | 144 | 180 |
| 176 | 211 | 141 |
| 288 | 288 | 374 |
| 144 | 72 | 302 |
At a level of significance of .01, is the difference in the number of lines of code due to language?
A comparative study of word processing software was modified to account for different types of keyboards: enhanced keyboard, modified keyboard, and standard keyboard. Keyboard layout and type of software could not be assumed to be independent, because certain software capability may be enhanced by particular keyboard layout. Therefore a 3x3 factorial design was implemented using 27 subjects, 3 in each treatment condition. The table below provides the completion time in minutes for a particular task. You may assume 1) all subjects had equivalent skills, 2) all subjects were trained to the same base level in the use of software, and 3) trained to the same base level in the user of the keyboard.
| Software Type | |||
|---|---|---|---|
| Keyboard Type | Menu-Driven | Command-Driven | Mixed |
| Enhanced | 9, 8, 10 | 8, 7, 7 | 8, 10, 10 |
| Modified | 14, 14, 13 | 10, 14,12 | 12, 10, 14 |
| Standard | 15, 18, 17 | 18, 16, 15 | 15, 15, 14 |
Is there a difference in the three word processing programs, as measured by the productivity of secretaries, at the .05-level?
Do the different keyboards affect the productivity of secretaries at the .05-level?
Is there a significant interaction between software type and keyboard type at the .05-level?
Upper management continues to push for the adoption of a cost estimating strategy for software projects. Under the direction of the CIO, we devised an experiment in which eight different, experienced project managers applied three different techniques to the same projects. The table below contains the data for the experiment. The outcome variable is the number of man-months estimated by the technique.
| Technique | |||
|---|---|---|---|
| Project Manager | 1 | 2 | 3 |
| 1 | 67.2 | 75.3 | 70.1 |
| 2 | 63.5 | 72.1 | 68.7 |
| 3 | 50.8 | 65.1 | 62.5 |
| 4 | 71.3 | 78.8 | 71.8 |
| 5 | 78.1 | 79.9 | 79.0 |
| 6 | 69.5 | 74.8 | 64.3 |
| 7 | 74.6 | 79.6 | 70.8 |
| 8 | 70.1 | 76.8 | 69.8 |
Do the data provide sufficient evidence to indicate that there is a difference in the effectiveness of the three techniques? Use .05.
Is there a significant difference due to blocks at the .05-level?
Engineering has completed the design of a handheld security device that will be sold to DoD contractors. The unit contains a battery to sustain volatile memory over time. There are four battery supplies whose products you are considering. Past experience indicates that battery lifetimes are normally distributed. You conduct an experiment using six batteries of each brand. Each of the batteries are placed in a test device that slowly drains the battery power and records the number of hours the unit provide power.
| Brand 1 | Brand 2 | Brand 3 | Brand 4 |
|---|---|---|---|
| 41 | 32 | 35 | 33 |
| 35 | 37 | 30 | 27 |
| 48 | 46 | 24 | 36 |
| 40 | 53 | 26 | 35 |
| 45 | 41 | 28 | 27 |
| 52 | 43 | 31 | 25 |
Does the data support or reject the null hypothesis, at the .01 level, that average battery lifetimes are the same?
What issues would you raise regarding the conduct of this experiment?