Skip to content

Technology vs Tables and Rounding Mistakes

Joe,

Two important points you bring up:

  1. Do not round intermediate values in a string of calculations. Wait until the very last step/answer to round to the number of decimals required by MyStatLab. On this problem and many others in this course, rounding too early can lead to wrong answers.

In the instructor view, I can cycle through the variations of that problem different students might see. On about half, I could round the z value to two decimal places and still get the correct answer. But for the one shown, I get the wrong answer. On all of them, if I round the standard error, sigma x-bar, to three decimal places, I always got the wrong answer. Rounding early is tempting if you are using a calculator and writing down the intermediate values instead of storing them in the calculator’s memory, if that is possible for your calculator.

  1. All tables today are created using technology, not the reverse. So do not delude yourself into thinking the tables are more accurate. If you enter the normal table on this problem with the rounded z of -2.02, you will get the wrong answer unless you interpolate between the table values. Note: on some problems where MyStatLab does not tell you to use the tables, it may accept the nearest table value (intersection of highlights). But if the problem says, “Use technology,” the approximate table value will be counted wrong.

Technology vs Tables and Rounding Mistakes

Rounding in MyStatLab

I get frequent emails from students complaining that they had the right answer, but MyStatLab did not give them credit. Often, when I am reviewing their claim, I find that they did not enter the… Rounding in MyStatLab

StatCrunch Tutorial Videos

StatCrunch logo (home)

StatCrunch is a great statistical analysis app that resides on the web and thus works equally well for both PC and MAC users. If you are taking a stats course and do not have good Excel skills, I suggest you consider learning to use StatCrunch. My sense is that students find StatCrunch’s learning curve, the time and effort needed to get up to a reasonable skill level, is much shorter and not as steep as learning both basic Excel skills and how to use Excel’s statistical formulas to crunch the numbers. This is especially true for short time frame, i.e. 8-week term, introductory statistics classes.

StatCrunch homepage If you bought access to MyStatLab, which has StatCrunch embedded, you should be able to use your Pearson MySTatLab to log in here. If you no longer have access to MyStatLab, you can purchase a 6 or 12 month access key for $13.75/$24.20.

StatCrunch Examples: If you prefer written instructions, this page contains links to StatCrunch Tutorial Videos