Acceptable Standard Deviation (SD)

How to Subscribe
MLS & MLT Comprehensive CE Package
Includes 147 CE courses, most popular
$95Add to cart
Pick Your Courses
Up to 8 CE hours
$50Add to cart
Individual course$20Add to cart
Need multiple seats for your university or lab? Get a quote
The page below is a sample from the LabCE course Quality Control. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

Learn more about Quality Control (online CE course)
Acceptable Standard Deviation (SD)

  • A smaller SD represents data where the results are very close in value to the mean. The larger the SD the more variance in the results.
  • Data points in a normal distribution are more likely to fall closer to the mean. In fact, 68% of all data points will be within ±1SD from the mean, 95% of all data points will be within + 2SD from the mean, and 99% of all data points will be within ±3SD.
  • Statisticians have determined that values no greater than plus or minus 2 SD represent measurements that are more closely near the true value than those that fall in the area greater than ± 2SD. Thus, most QC programs call for action should data routinely fall outside of the ±2SD range.