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Showing posts from October, 2009

Reliability Calculations in Excel

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In Operations Management today we used Excel to calculate product reliability. Reliability is defined as "the ability of a product, service, part, or system to perform its intended function under a prescribed set of circumstances" (Stevenson, 2009). In order to calulate reliability over a given length of time we need to use the following formula:

P(no failure) = e-t/MTBF

where:

e = 2.7183
t = Length of service before failure
MTBF = Mean Time Between Failures

One of the cases we did in class involved an auto detailing company that wanted to calculate the reliability of its vacuum cleaners. Excel provides an "EXP" funtion that we can easily apply here. After entering all data for the problem as shown on the spreadsheet below, we type the formula =EXP(-A5/$B$2) in cell B5 and copy down. Next we plot the distribution for t=0 to the maximum life expectancy of 20 years using a line graph. What we end up with looks like a classic case of "exponent…

Five Things to Know Before You Upgrade to Windows 7

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October 23, 2009 (PC World) - Now that Windows 7 is here, the three out of four users who have rejected Windows Vista and clung to the tried and true Windows XP can breathe a sigh of relief and consider moving to the new flagship operating system.

Upgrading or switching operating systems often comes with some trials and tribulations and the Windows 7 upgrade is no exception. Microsoft has tried to provide the tools users need to make the transition as easy as possible, but you may hit some snags. Here are five things you should be aware of as you upgrade from Windows XP to Windows 7:

1. You can't upgrade directly. Unfortunately, Microsoft has not provided Windows 7 with the capability to upgrade directly from Windows XP. The explanation is that so much has changed between Windows XP and Windows 7 within the operating system kernel itself, the Registry, the drivers, etc. that trying to get from Point A to Point B just won't work.

That isn't as horrible as it sounds. Frankly, …

Excel Solver for Business Decisions

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Today in Operations Management we did a case study using the Excel Solver "Add-In." In this example the company sells three products (A, B, and C). An Income Statement calculates the profitability of each product and the goal is to "maximize" profit for the entire company given the constraints on Labor Costs, Materials, and Sales.

Students were required to enter all of the information from the case into the spreadsheet and then configure the Solver parameters in order to come up with a solution. The "Target Cell" is of course, profit. The "Changing Cells" are the "optimum" number of units of Product A, B, and C that will be produced as determined by the Solver. Constraints include how much of each resource is available as well as how many of each product can be sold at best.

Once everything was entered, all that needed to be done was to click the "Solve" button and let Excel find an answer. The model assumes the solution wi…

Patch Day

October 14, 2009 (AP) - Microsoft Corp. issued a record number of security patches for its software Tuesday as part of its regular monthly update.

The software maker plugged 34 holes and designated most of them "critical," Microsoft's most severe rating. Among them are fixes for Windows Vista, Windows XP, Windows 2000 and even Windows 7, which doesn't go on sale to consumers until Oct. 22 but has been in use by early testers and software developers. (Msnbc.com is a NBC Universal-Microsoft joint venture.)

The patches target a wide array of Microsoft software, including the Internet Explorer Web browser, Media Player, Outlook and the Silverlight technology underlying multimedia Web sites.

Security researchers at McAfee Inc., which makes antivirus software, noted that many of the holes addressed Tuesday are dangerous because they expose regular PC users to harmful programming code when they visit rigged Web sites or play media files that have been tampered with.

Consumers…