If you have ever attended one of my Excel classes, you will have heard me repeat (and repeat and repeat) the importance of formatting your data. Do not let Excel ‘plonk’ your data into whatever category it thinks right. Most of the time, Excel will guess correctly, but not always. Text input will be put into a General format, unless you otherwise specify. Zip codes will also be put in the General format. Dates will be put into the default short date format, assuming that you have entered the data in a way that Excel recognizes as a date. So why worry about the format at all? Broadly speaking, there are two reasons:
1) In Excel, there will be times when particular functions and formulas will not work properly because there is a format mismatch. For example, you may be trying to count a field that Excel considers a text field, but you think is a number field (based on how the data looks). In this example, using the COUNT() function will not work–you need to use the COUNTA() function. But any scenario that involves formatting in Excel is, in theory, fixable with a little attention to detail. In other words, make sure that you format your data properly.
2) In the news recently, there was a sad story about the consequences of formatting. I am referring to Patient 0 of the AIDS epidemic. At the time when AIDS was first being identified, the Center for Disease Control and Prevention (CDC) conducted a research survey trying to figure out what was causing AIDS. In interviewing men with the disease, it became apparent that many of them had a single partner in common, Gaetan Dugas. In the documentation for the research, the CDC scientist designated Dugas as Patient O (as in Outside California). NOT 0, as in 0,1,2,3…From this data formatting misreading arose a whole myth around Gaetan Dugas–that he callously spread the disease. That he, single handedly, was responsible for the beginning of the AIDS epidemic. Poor man. His reputation was trashed because of a formatting misunderstanding.
So, if you think that formatting is not significant, think again! It can, truly, be life-altering.