Statistical Forensics
One Digit Too Many!
When the original handwritten data contain only three  decimal places, and the same data entered into a Microsoft Excel7  spreadsheet appear with four decimal places, there is cause  for suspicion. Where did that extra digit come from? And when that  fourth digit is either a zero or a five, (and no other  digit, e.g., one or nine) the suspicion is that division  by two produced the fourth decimal digit. Thus, division  by two of a decimal number whose last digit is odd  leaves a remainder of one-half which produces an extra decimal  digit, five. In contrast, when the last digit is even, there  is no remainder and the extra digit is zero. Division by  two yields no other extra digits.
In one case, these clues led investigators of ORI's  Division of Investigative Oversight (DIO) to determine that the  data for a third rat were fabricated by averaging the data for two  others. This case concerned a study of the effect of rhythmic contractions  of skeletal muscle in the hind limbs of rats where blood flow was  measured at rest and during nerve stimulation. Measurements of blood  flow and muscle weight were recorded.
The respondent presented results for six rats in a  lab seminar. Sometime after that, a co-worker discovered that the  original data sheets for two rats were blank. The respondent furnished  the university with copies of tracings of continuous measurements,  handwritten recorded data for muscles for six rats, and printouts  of a Microsoft Excel7  spreadsheet that contained blood pressure measurements and muscle  weights for six rats.
DIO investigators concentrated on the measurements  of muscle weight. The investigators observed that the entries in  the spreadsheet for Rat-3 and Rat-6, purportedly copied from the  handwritten data sheets, had an extra decimal digit. Therefore,  the spreadsheet numbers had not been copied from the handwritten  sheets. They further observed that the extra digit was either five  or zero. This observation led to the hypothesis that the  Rat-3 and Rat-6 measurements were the average of two measurements.  Investigators then verified that the purported measurements for  "Rat-3" and "Rat-6" were the averages of the  corresponding measurements, respectively, for Rat-1 with Rat-2,  and Rat-4 with Rat-5. This irrefutable demonstration that the weights  for both Rat-3 and Rat-6 were fabricated by calculation facilitated  the voluntary exclusion of the respondent from receiving Federal  funds for 3 years.