Working Scientifically

Question 1

What are random errors

Answer 1

• Random errors will shift each measurement from its true value by a random amount and in a random direction
• These will affect reliability (because their random) but not the overall accuracy of the experiment
• Different random errors include
• Reaction time: any experiment where reaction time is involved
• Parallax: the angle you view a dial (only random if you view from a random angle)
• Measurement errors with insufficient precision: rounding up 10.25 mm on a ruler

Question 2

What are systematic errors

Answer 2

• Systematic errors will shift values from their true value by the same amount or fraction in the same direction each time
• These do not affect reliability (since they’re always the same) but do affect accuracy
• Usually arise from problematic or incorrectly used equipment
• Different types of systematic errors:
• Scalar error: If a piece of equipment is not calibrated (e.g. a wooden ruler has shrunk), all measurements will be offset by the same amount
• Zero error: If a piece of equipment has an offset (e.g. mass balance shows a non-zero reading when nothing is on it), all measurements will be offset by the same amount

Question 3

What is validity

Answer 3

• Validity relates to the experimental method and how appropriate it is in addressing the aim of the experiment
• Several aspects relate to validity: the equipment, the experimental method and the analysis of results
• Relates to use of independent, dependent and controlled variable

Question 4

What is reliability

Answer 4

• Reliability relates to how close repeated measurements are to each other
• Can consider reliability of the experiment or reliability of a measurement
• Reliability can affect the overall validity of the experiment

Question 5

What is accuracy

Answer 5

• Accuracy is how close the final result is to the correct or accepted value
• Use of better equipment will improve accuracy as this will reduce systematic errors
• Compare measurement value to accepted value

Question 6

What is precision

Answer 6

• Precision refers to the maximum resolution or the number of significant figures in a measurement
• e.g. a clock has precision of 1 s whereas a stopwatch has precision of 0.01 s
• Accuracy does not rely on precision