Paper 5

Question 1

2 calculations to do T test

Answer 1

• Mean
• SD

Question 2

T test key phrases

Answer 2

-when comparing means of 2 sets of data/continous/quantative data
- If T value is GREATER than critical value, results are sig and NOT due to chance
- go with larger degree of freedom if its a range e.g if DOF is 19 and table range is 18-20, take 20

Question 3

Degrees of freedom

Answer 3

• N-1
• if theres 2 samples then (n-1) + (n-1)
• n= number of samples

Question 4

Data needed to calc SD

Answer 4

• Number of samples
• Mean value

Question 5

SD key phrases

Answer 5

• spread of data from mean value
• larger the value = less reliable results
• if spread of data around mean is NARROW spread = more reliable than wide sp
• Overlapping= no sig diff between means

Question 6

Chi squared test

Answer 6

• Shows data is discrete/discontinous
• if chi sq value SMALLER than critical value at 0.05 theres is NO sig diff + results due to chance+ accept null

Question 7

Standard error, Sm key phrase

Answer 7

• SE = *calculate confidence limits + indicates how certain you can be that the “true” mean lies within the range of est mean sample *(like guessing the average height of all students in a school by measuring just a few. The SE tells you how good your guess might be. If the SE is small, your guess is likely to be very close to the true average height. If it’s large, your guess might be off)
• Measure of accuracy of calculated mean value/closeness of sample to actual mean
• The larger SE= less reliable the value
• A close sample mean = shows results are close to actual mean

Question 8

Error bars

Answer 8

• If SE bars DON’T overlap = diff between samples, results are SIG and NOT due to chance
• If SD values/SE bars overlap= no sig diff between data + due to chance

Question 9

Spearmans correlationn use

Answer 9

• If data NOT normall distributed
• Data points indepent of each other
• data can be converted to ordered data
• if value closer to 0 = weak pos correlation between distribution of 2 species.

Question 10

Pearson correlation

Answer 10

• data collected is continous/normal distributed/linear

Question 11

Microscope

Answer 11

• Magnification of x400
• use EPG
• calibrate eye piece w stage micrometer
• find value in mm of EPU
• CONVERSION OF MM/EPU TO UM

Question 12

PLANNING AN EXP

Answer 12

• IV and how to vary it
• DV and how to measure
• 2 control V’s
• What is the control e.g light vs no light
• Risk, low/med/high and how to prevent injury
• Reliability/repeats + stats test
• Accuracy- range of solutions

Question 13

If asked about inaccuracy

Answer 13

• insufficent data
• narrow range of conc w smaller intervals within range
• more conc/temps
• have control so comaprison can be made
• inconclusive results if NO stats test carried out

Question 14

CO2

Answer 14

• Usually, most of the CO2 absorbants are with -OH eg: NaOH or KOH
• Sources of CO2 are CaCO3, H2CO3
• a non-chemical source: gas cylinder
• the gas is supplied through a bubbler.
• to measure CO2 concentration: use probe with meter/gas syringe

Question 15

Measuring:

Answer 15

• use mm calipers
• a ruler- calibrated to cm or mm
• measuring cylinders
• syringe, pipette
• weighing scale/ electronic balance
• digital/mercury thermometer
• MEASURING PLANT LENGTH

Question 16

MOVEMENT AND TIME

Answer 16

1. measure distance moved at a certain time (or)
2. measure time taken for certain distance moved

Question 17

Control:

Answer 17

• in an exp with living organisms, the control must be a dead organism
• whatever factor is being used in the question is emitted from the control
• For counting chromosomes and making them visible, the growing regions of the plant are cut
• cut surface of the specimen
• chromosomes are counted by placing cut surface under a high power light microscope(with high magnification)
• How to make chromosomes visible?
• > add dye/stain them

Question 18

outline how colorimters should be prepared before carrying out measurements

Answer 18

1. calibrate colorimeter / set colorimeter (absorbance) to zero ;
2. use distilled water (to, calibrate colorimeter / set to zero) ;

Question 19

for risk assesment what are the things you MUST state

Answer 19

• the hazard e.g knife or reganet
• the risk e.g injury/irritant etc
• precaution e.g cut away from hand/wear gloves

Question 20

suggest why results of the exp should not be interpetredt as FINAL

Answer 20

1 investigation only, carried out once / not repeated ;
2 investigation only on one crop species
3 investigation only investigated, one / two, gene
4 investigation only, in one geographical area ;
6 no long-term data / no data over several generations ;

Question 21

CORMMS abt stomatal density

Answer 21

• method of, random / systematic sampling of plants ;
• (take leaves) from same species, that is present in both habitats ;
  -collect a minimum of 5 leaf samples (in both habitats) ;
  -same position / age, of leaf (on plant) ;
• impressions to be taken from, lower / upper / both / same, surface(s) (of leaves) ;
• (impressions viewed using) same, magnification / lens / size of field of view ;
  -count stomata (in field of view) ;
• details of systematic counting / count only whole stomata / take a photograph and mark ;

Question 22

why extract fecal matter sample instead of plasma sample

Answer 22

• no invasive
• can be collecetd remotly
• doenst harm organism
• no risk if infection

Question 23

how to seperate liquid from solid

Answer 23

• make suspension/liquidy X
• centrifuge/filter to remove solid

Question 24

null hypothesis for chimps life expactcy w SIV and w/o SIV

Answer 24

no difference between the, life expectancy between SIV+ and SIV-

Question 25

explain whats meant by p<0.05

Answer 25

• probability / it, is where null hypothesis is rejected ora ;
• less than, 0.05 / 5% / 5 in 100, probability that the, result / it, is not significant / is due to chance ;
• more than, 0.95 / 95% / 95 in 100, probability that the, result / it, is significant / is not due to chance

Question 26

how to calc percentage change

Answer 26

• initial-final/inital x 100

Question 27

define percentage density

Answer 27

• number of X per unit area

Question 28

Dilution formula: C1V1= C2V2

Answer 28

C1= Concentration of the stock solution (6.0%)
- V1 = Volume of the stock solution to use
- C2 = Desired concentration of the final solution
- V2 = Final volume of the solution (50 cm³)

Question 29

How to know if reuslts are sig or not

Answer 29

If the p-value is less than 0.05, = results are significant.
- reject the null hypothesis,
- not due to chance

Question 30

suggets why scientist calculated a 95% confidence interval

Answer 30

• to get a measure of how close the, calculated /, mean is likely to be to the, true mean
• if no overlap of error bars the results sig and vice versa
• shorter, error bars show true mean is likley to be closer to the calculated mean