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A-level Biology Oxford AQA > Practical Skills > Flashcards

Flashcards in Practical Skills Deck (51)
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1

What is a prediction/hypothesis?

Specific testable statement about what will happen in experiment

2

Define precise results

Results that don't vary much from mean

3

Define Valid

Free of error

(Valid results answer original question)

4

How do you obtain valid results?

By controlling all variables to make sure you're testing thing you want

5

Define accurate results

Results that really come close to the true value

6

What can decrease accuracy of results?

Human interpretation of measurement (e.g. determining colour change)

7

How can precision be reduced?

Reduced by random errors

8

Define Reproducible 

If someone different does experiment, using slightly different method or piece of equipment, results will be the same

9

Define Repeatable 

If same person repeats experiment using same methods and equipment = get same results

10

Define Calibration 

Marking a scale on a measuring instrument

11

Define Resolution

Smallest change a measuring instrument can detect

12

Define a zero error

Systematic error caused by using equipment that isn't zeroed properly

13

Define a random error

Unpredictable way in which all measurements wary

(e.g. human errors in measuring)

14

How can you reduce the effect of random errors

By repeat readings & finding the mean

15

Define a systematic error

Measurement wrong by same amount every time

16

Define a measurement error

Difference between measured value and true value

17

Define uncertainty

Amount of error your measurements might have

18

How can you calculate a percentage error of your measurements?

19

Name 2 ways you can reduce uncertainty

  1. Using most sensitive equipment available
  2. Measure a greater amount of something

20

Define categoric variables 

Values that are labels e.g. names of plants

21

Define nominal variables 

Type of categoric variable where there is no ordering of categories

e.g. red flowers, pink flowers, blue flowers

22

When is it suitable to use a scatter graph?

When you're looking at relationship between 2 discrete/independent variables

23

Name 2 reasons why have a control group with a placebo makes your results more reliable

  • Removes researcher biasis
  • Control group can't show psychologial effects

24

Data is often given as percentages of people dying from each cause.

Explain the advantage of giving these data as percentages. (2)

  • Easier to compare if sample size effectively the same
  • Different no. of people in each group

25

If experimental group are given the treatment via injections, suggest how the control group should be treated (2)

  • Given only saline
  • Otherwise treated exactly the same way

26

What does standard deviation tell you?

Spread from the mean

27

Comment on the effectiveness of taxol when used separately and as a combined treatment (related to SD)

SD overlap for OGF with taxol and taxol on its own so not conclusive/could be chance/both treatments effective

28

Why should you repeat experiments?

  • To increase the reliability of your results
  • Anomalies can be identified

29

What does an overlap in standard deviation mean?

Unlikely that any difference (in results) is significant

30

An investigation was carried out into the effect of carbon dioxide concentration and light intensity on the rate of photosynthesis in a species of plant. The temperature was kept constant during the investigation. Explain why. (2)

  • Temperature affects the rate of photosynthesis
  • ∴ any change in photosynthesis rate is the result of CO2/light intensity

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