Biology Practical Skills: Sources of Error

Flashcards covering experimental vs. human errors, specific biological practical errors, and suggested improvements for lab investigations.

Experimental errors

Errors inherent in the process of taking experimental readings that cannot be eliminated by repeating the experiment, only minimized.

Human errors

Errors that occur due to carelessness, reading instruments wrongly, or not following instructions; these can be eliminated when precautions are taken.

Environmental conditions

Factors such as wind, temperature, and humidity that can influence the experimental set-up and cause experimental errors.

Parallax error

A form of human error caused by reading an instrument wrongly from an incorrect eye position.

Precision Improvement (Volume)

Using a burette or different syringe sizes, such as $1\text{ cm}^3$ or $5\text{ cm}^3$, when an instrument is not precise enough for small volumes.

Color standard

A guide used to determine the final color of a mixture to reduce subjectivity in end-point determination.

Colorimeter

A relevant instrument used to determine the final color of a mixture for a quantitative reading.

Relationship Observation Improvement

Using a narrower range of $pH$, temperature, or concentration, or testing at more frequent intervals to observe variables more accurately.

Sample size improvement

Increasing the number of specimens tested to reduce error caused by a sample size that is too small.

Specimen Consistency (Citrus Fruit)

Ensuring fruits used in an investigation are of the same age and ripeness to avoid experimental error.

Ascorbic acid (Vitamin C)

An antioxidant that reduces iodine to iodide, preventing iodine from forming a colored complex with starch molecules.

Iodine Quantification Error

The inaccuracy of counting drops where the volume in each drop may be inconsistent; improved by using a syringe or burette.

Gas syringe

An instrument used to measure the volume of gas per minute to improve results when bubble sizes are not uniform.

Thermostatically controlled water bath

An improvement used to keep temperature constant when the water in a beaker decreases over time, affecting rates of respiration.

Sealant (e.g. petroleum jelly)

A substance added around rubber bungs to ensure seals are fully airtight in respiration experiments.

Simultaneous counting error

A source of error in respiration experiments involving two cultures; improved by conducting the experiment for each test tube separately.

Foam extraction error

Accidentally sucking foam into a syringe instead of the yeast suspension; improved by using a larger volume or placing the syringe near the bottom.

Stirring with thermometer

A modification to improve results by ensuring even temperature distribution before taking a reading.

Replication

The process of repeating an experiment to take an average reading, which improves the reliability of the results.