Experimental language and techniques

Question 1

accurate

Answer 1

a measurement is considered accurate if it is judged to be close to the true value

Question 2

precise

Answer 2

-a precise measurement is one in which there is very little spread about the mean value

-precision depends only on the extent of random errors, and gives no indication of how close results are to the true (accurate) value

Question 3

random error

Answer 3

-unpredictable differences in results due to poor measurements being made

-usually because of not carrying out exactly the same method each time, or because of limitations of the measurement device

Question 4

How can the effects of random errors be reduced?

Answer 4

take more readings, ignore anomalies and calculate mean value

Question 5

repeatable

Answer 5

a measurement is repeatable if the original experimenter repeats the investigation using the same method and equipment and obtains the same/precise results

Question 6

How could you check if an experiment’s results are repeatable?

Answer 6

repeat experiment and see if the results are similar

Question 7

reproducible

Answer 7

a measurement is reproducible if the investigation is repeated by another person using different equipment and the same results are obtained

Question 8

systematic error

Answer 8

causes readings to be a different to the true value by a consistent amount each time

eg blood pressure measurements if just before the measurements were to be made, something always caused the blood pressure to go up (like stress)

Question 9

valid

Answer 9

the suitability of the investigative procedure to answer the question being asked

Question 10

What is the difference between a zero error and a systematic error?

Answer 10

All zero errors are systematic errors, but not all systematic errors are zero errors

-zero errors are always caused by the measuring equipment (eg not pressing tare before measuring the mass of something in a container)

-systematic errors can be zero errors, or when there is a bias caused that always changes the recorded value by a certain amount (eg just before blood pressure was measured, something always caused it to go up, like stress)

Question 11

How many tests should you do in an experiment?

Answer 11

ALWAYS AT LEAST FIVE

Question 12

What is an anomalous result?

Answer 12

a result that doesn’t fit in with the general pattern of the other results from an experiment

Question 13

When you are asked for the reason behind an anomalous result, what is a good backup if you can’t think of anything else?

Answer 13

-error in reading equipment
-BE SPECIFIC
-eg misread the measuring cylinder scale

Not always accepted though, for example if it is a digital meter - usually try to get something better than this

Question 14

Why are multiple readings often taken in an experiment?

Answer 14

-to spot any anomalous results
-to calculate a mean and reduce the effect of random errors

Question 15

Why might using a metre rule be worse than using a digital calliper to measure something?

Answer 15

-metre rule has a lower resolution
-therefore it is less accurate

Question 16

How do you calculate uncertainty for a set of data?

Answer 16

calculate the range and divide by 2

Question 17

What is a model?

Answer 17

an idea used to explain observations and data

Question 18

Why might scientists use different models for the same phenomena?

eg light wave-particle duality

Answer 18

different models may be appropriate to use in different situations, as one model might not explain all observations

Question 19

Why might a new model replace an old model?

Answer 19

-new evidence is seen in experiments which can’t be explained using the old model
-a new model might explain these new observations

eg Big Bang theory, nuclear model replacing Plum Pudding, geocentric to heliocentric solar system

Question 20

Why is peer review an important process?

Answer 20

it helps to detect false claims, bias, and inaccurate data to check its validity

Question 21

Why can’t these measurements show that the temperature sensor gives precise readings?

Answer 21

measurements have not been repeated for each surface to show that they cluster together closely