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A2 > Paper 5 > Flashcards

Paper 5 Flashcards

1
Q

When should a t-test be used?

A

To compare 2 means of continuous, normally distributed data

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2
Q

When is Pearson’s linear coefficient used?

A

To correlate two sets of continuous, linear and normally distributed data

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3
Q

When is chi squared test used?

A

To compare the observed against the expected frequencies

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4
Q

When is Spearman’s rank coefficient used?

A

To correlate ordinal data, which can be ranked and is not continuous

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5
Q

How are the degrees of freedom for t-test calculated

A

(n1-1)+(n2-1)

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6
Q

How are the degrees of freedom for Pearson’s linear coefficient calculated?

A

Number of pairs of data-2

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7
Q

How are the degrees of freedom for chi-squared test calculated

A

Number of categories -1

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8
Q

How are the degrees of freedom for Spearman’s rank coefficient calculated?

A

Number of pairs of data -2

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9
Q

Statistical conclusion phrasing

A
  1. State calculated value is smaller/larger than critical value at p=0.05
  2. There is less/more than 5% probability that the results are due to chance
  3. The results are/are not statistically significant
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10
Q

What does standard deviation measure

A

Spread of data

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11
Q

What does standard error measure

A

The reliability of the sample mean- how close the calculated mean is to the true mean

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12
Q

What is the range of error bars

A

+/- 2 x standard error

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13
Q

Why is percentage change calculated instead of actual change

A

May not have the same starting value, percentage change allows for a valid comparison to be made by showing the proportional change

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14
Q

Statistical test for biodiversity

A

Simpson’s index of biodiversity

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15
Q

What does the calculated value in Simpson’s index indicate

A
  • It is between 0 and 1
  • Closer to 1 indicates higher biodiversity
  • Closer to 0 indicates lower biodiversity
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16
Q

Function of stage micrometer

A

Used to calibrate eyepiece graticules

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17
Q

Function of eyepiece graticule

A

Can be calibrate to make measurements, and can be used to draw structures proportionally

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18
Q

When are bar charts used

A

When the independent variable is qualitative

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19
Q

When are histograms used

A

For continuous data that is divided into classes

20
Q

What is a systematic error

A

An error that is consistently repeated throughout the experiment

21
Q

What is a random error

A

An unpredictable error with no patterns

22
Q

How can the reliability of results be increased

A

By repeating the practical at least 3-5 times and taking a mean- identify and exclude anomalies

23
Q

How can temperature be better standardised

A

By using a thermostatically controlled water bath

24
Q

How can the accuracy of measurements be improved

A

By using apparatus with smaller divisions

25
Q

5 components that should be in practical plan

A
  1. controlled variables
  2. independent variables
  3. dependent variables
  4. how to improve reliability
  5. safety
26
Q

safety- what to write

A
  1. state the hazard and the level of risk
  2. state a safety precaution to take
27
Q

dependent variable- what to write

A
  1. identify the dependent variable
  2. describe how it is measured and the apparatus needed
28
Q

important procedures when setting up potometer

A
  • male slanted cut of shoot underwater
  • make sure apparatus if airtight
  • use syringe to adjust gas bubble position to starting point
29
Q

important procedures when setting up a respirometer

A
  • make sure the apparatus is airtight
  • air must be replaced between each set up
30
Q

random sampling procedure

A
  • make a grid using measuring tape
  • use random number generator to obtain sets of coordinates
  • place quadrats at coordinates
31
Q

chromatography procedure

A
  • draw pencil line at base of thin paper
  • use a capillary tube to drop the extract onto the origin
  • dry and repeat to concentrate spot
  • dip in solvent
  • cover solvent with bung to prevent evaporation
  • after running the solvent, allow chromatography paper to dry
  • calculate Rf
  • compare Rf with known Rf values
32
Q

preparing slide sample

A
  1. obtain required sample by cutting with scalpel/peeling with forceps
  2. Mount on a slide and add stain if necessary
  3. Squash by placing a cover slip on and pressing down gently
33
Q

What is soda lime used for

A

To absorb carbon dioxide

34
Q

How can light intensity be altered- photosynthesis prac

A

The distance of the light source from the plant

35
Q

How can temperature be altered- for photosynthesis prac

A

changing the temperature of the water bath the test tube sits in

36
Q

How can carbon dioxide be altered

A

The amount of sodium hydrogen carbonate dissolves in the water the pondweed is in

37
Q

Why are 95% confidence intervals calculated?

A

95% probability that the actual mean population lies within the range

To test whether the means are significantly different

To get a measure of how close the calculated mean is likely to be to the true mean

38
Q

What do the length of error bars indicate

A

Shorter error bars show that the true mean is likely to be closer to the calculated mean

Longer error bars show that the true mean is likely to be further away from the calculated mean

39
Q

Outline how the population size of beetles can be estimated

A
  1. Mark release recapture technique
  2. Trap beetles and mark using a marker
  3. Re-trap the beetles
  4. Use lincoln index to estimate population size:

(number in first sample x number in second sample)/marked number in second sample

40
Q

Why is standard deviation calculated

A
  1. Shows the spread about the mean
  2. Indicates the reliability of the data
  3. To put error bars on the graph, see if the standard deviations overlap
41
Q

Why may a conclusion not be valid

A

Only 2 (concentrations) measured
no repeats
no statistical analysis
lab conditions may not be replicated in the field

42
Q

Describe two ways the students can obtain the measurement needed to work out the results per unit area of leaf

A
  1. measure radius of area of leaf then use pi(r)2
  2. use transparent grid on the area, count squares
43
Q

Advantages of finding standard deviation

A
  1. shows the spread of data about the mean
  2. allows calculation of confidence intervals
  3. allows determination of whether or not there is a significant difference between mean values 4. allows t test to be calculated
  4. to plot error bars on graphs
44
Q

Why is conclusion not valid- pearson

A
  1. correlation does not mean causation
  2. fewer than the number of paired observations recommended
  3. no replicates, only done experiment once
  4. narrow range of (IV)
45
Q

how to calculate volume of oxygen uptake in tube

A
  1. measure radius
  2. use pi(r)2 to find area
  3. multiply by distance in mm
46
Q

RQ value of germinating seeds practical

A
  1. add fixed number of peas to respirometer
  2. a control containing glass beads of the same mass
  3. insert bung with tubing with clip and glass tubing with scale so that the apparatus is airtight
  4. dip the glass tube into coloured liquid
  5. place respirometer tube into a water bath at 15 degrees
  6. open clip and allow to equilibrate
  7. close the clip, mark position of dye and start stopwatch immediately
  8. measure the movement of dye on the scale for 5 minutes
  9. open clip and reset coloured liquid
  10. minimum of 3 measurements and take mean
  11. removing carbon dioxide absorbent
    12.medium risk, carbon dioxide absorbent is an irritant, wear gloves
47
Q
A

A2 (3 decks)

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