Tutorial 12
Hints
A few suggestions that may improve yourlab grades

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Well, you've come to end of the Excel tutorials for Biology lab students. I hope that you have found them useful and informative. But before we conclude, let me offer you a few helpful hints that may make your lab experience a more satisfying one.

Work carefully. One of the exhilarating aspects of a Biology lab course is that once your experiment has concluded and you have left the lab room, you can not double-check your recorded data. Take your time and make careful measurements and have all lab partners verify these measurements. (Here I am reminded of the old woodworker's rule: Measure twice, cut once.)

When recording values in your notebook or data table, be careful to transcribe the correct values. Confer with your lab partner(s) before leaving the lab that your recorded data is correct.

Neatly display your work. Use Excel to make your data and data analysis attractive and easy to read (even if it's only for your own use). Create titles and headings to clearly show what the data represents. Label your data columns with the correct units. Use the appropriate number of significant figures. Also emphasize important text by making it bold and adding borders. Shade cells that contain formulas.

Display sample formulas. You will occasionally be asked to show your work in a table. While this is not appropriate for formal tables in lab reports, it is very useful for your own data and calculation tables. If you show your work by displaying sample formulas for each group of formulas on your worksheets, your instructor, TA, and lab partners will be able to follow your work and identify errors. Shade the cell to make the displayed formula even more noticeable. Notice in the example below that you can simply add this information along side the formal table that you will add to your report.

Check your work by hand. Don't trust your Excel formula to spit out the correct answer. It is quite easy (and common) to improperly use a spread sheet to perform complicated calculations. To prevent careless mistakes, double-check each group of formulas by hand, or with a hand-held calculator. By far the easiest way to do this is to enter data that you already know the results for. In the example below, making the x and y values equal should produce a slope of 1, intercept of 0 and an r2 of 1.000. It does! Now you can enter your data with confidence that your calculations are correct. Few things will improve the accuracy of your calculations as much as a simple formula check and putting known values in every cell is the only way to check the accuracy of the formulae as well as the accuracy of all of your copy and paste operations. Spot checking the arithmeticwont do that.

Reality check: Also, get in the habit of examining your final result by asking yourself, Does this answer seem reasonable? Although not every lab experiment will deliver small percent error values less than, say, 5%, it is safe to say that, if performed properly, your results should be within 50% of an accepted value. If your results showed huge error values, say 200%, chances are you either made a calculation error or did not perform the experiment properly. (See Hint #1 above.)

The reality check also serves as a unit check. You can get wrong results even with good math if you type in the rwong units. If your data sheet shows, for example, that the average surface area of a barley leaf is 35.76 M^2 you should suspect that you have selected the wrong units or have made a conversion error.

Printing tips. Here are some hints on printing your worksheet so your instructor can easily grade your report. They will be in a much better mood, you will look like you know what your doing and you grade will reflect it.

• Resize the rows and columns so data and text are easy to read.

• Consult the Page Setup menu to ensure that you print gridlines and the row and column headings when required and that you omit them when appropriate.

• Try to fit the data and any analysis on one printed page. There are several ways to do this.

  1. Make the font size smaller to enable more text to fit on the page.

  2. Decrease the page margins by clicking on File >> Page Setup >> Margins tab and adjusting the margin widths.

  3. If you have many columns, you may find that orienting the page in landscape mode (as opposed to portrait mode) is all that is needed. To do this, click on File >> Page Setup >> Page tab and change the orientation to Landscape.

  4. Finally, you can scale the page size and force Excel to print that entire worksheet onto one page. To do this, click on File >> Page Setup >> Page tab and either
     
     • Adjust the page size to some percentage of its normal size,

       or,

       

     • Fit the worksheet to a defined number of pages.

Whew, you made it!

You have reached the end of the Excel tutorials. I hope you have enjoyed the show. I am interested in hearing from you. If you have any comments and/or concerns about the format, usefulness or readability of these tutorials, please contact .

Thanks, and good luck to you in your Biology lab!

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Please send comments, problems or request for topics to

Walter I. Hatch
wihatch@smcm.edu
August 11, 2005