Human errors can be described as bumbling mistakes made during an experiment that can invalidate your data and conclusions. Scientists recognize that experimental findings may be imprecise due to variables difficult to control, such as changes in room temperature, slight miscalibrations in lab instruments, or a flawed research design. However, scientists and college professors have little tolerance for human errors occurring due to carelessness or sloppy technique. If you know you really messed up, redo the experiment.

Failure to Follow Directions

Before leaping into a laboratory activity, carefully read the instructions in the lab manual thinking about the purpose of the experiment and possible results. If you don’t understand a step, consult with your lab partner or instructor before proceeding. Perform each step of the experiment in the correct order to the best of your ability. Don’t attempt shortcuts in the procedure to save time. Conducting an experiment is similar to following a recipe in the kitchen but far more exacting. Even slight deviations can change your results in dramatic ways.

Mishaps in Measuring

Spilling chemicals when measuring, using the wrong amount of solution, or forgetting to add a chemical compound are mistakes commonly made by students in introductory science labs. Measurement errors can result in flawed data, faulty conclusions and a low grade on your lab report. Worse still, you may cause a dangerous chemical reaction. Ask your lab instructor for guidance if you know your measurements are way off from the instructions; sometimes the experiment or your calculations can be adjusted to avoid starting over. It is better to be safe than to risk injury to yourself and others.


Failing to maintain sterile conditions can cause contamination and produce unwanted results in your experiment. For example, coughing or breathing into the petri dish when inoculating nutrient agar with a certain type of bacteria can introduce other bacterial strains that may also grow on your culture. Mold spores and dust can harm your experiment if you forget to wipe down your work area with alcohol. Touching the tip of a pipette before using it to transfer liquids during your experiment can also affect results.


Data errors such as applying the wrong mathematical formula, miscalculating answers, or placing the decimal in the wrong place can adversely impact an experiment by skewing your results. Failure to carefully observe and record raw data can be problematic when later attempting to analyze your data. Keeping a detailed, written log of your lab activities can help you learn from your mistakes. Dartmouth University recommends that students keep a permanent lab notebook for documenting their techniques, procedures, calculations and findings for accuracy and quality control.