EMPA: Common Themes - created from Mind Map

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SAMPLE SIZE, REPEATS & ANOMALIES

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Large sample size

data for last 3 tubes more reliable than for 1st 3. Practice in judging when product appears/approximate time of curd appearance known, so able to watch more carefully at that time

Anomalies can be identified. Vice versa to check if a result is anomalous REPEAT experiment

More reliable mean

check results concordant (similar)

Minimise effects of variation in data

Representative

Allows statistical tests to be conducted

CONFOUNDING (CONTROL/KEEP SAME) VARIABLES

TEMPERATURE

pH

Other C variables/precautions/standardisations

If not controlled in investigation, how to find how it could've influenced results

Keeping it constant

Monitor room temp thru out/ at beginning & end of experiment

Water bath: more temp variation in air than water/it keeps test tubes at constant temp

Monitor with thermometer

use data-logger to record temp

Adjust with hot/cold water

Temp of water bath as reliable as possible: measure temp of bath at beginning & end of reaction period (or more) to assess effect of any temp changes during reaction/to show there was no/little variation in temperature

EQUILIBRATION

Leave tube 1 in water bath for 5 mins before adding enzyme. To equilibrate /for solution to reach the temp of bath

Keep constant: use buffer

If 2 enzymes with diff optimum pH, then use 2 buffers

Volume/mass

Concentration

Standardise type/category

Time: between readings;duration; mixing

All controlled apart from 1-independent variable

No./rate of repeats

Read meniscus at eye level

Allows comparison of results/reproduce-able (diff techniques but same results)/repeatable (exact same technique) by someone else

Investigating 1 variable only

Same end point each time

LIMITATIONS (UNCONTROLLABLE CONFOUND'N VARIABLES)

Difficult to time/measure accurately

Diffi to keep temp constant

Diffi to decide when product present /formed--subjective

Theres many variations (creeping in..) in 1 'type'

Everyone's judgement diff

CONTROL EXPERIMENT (TO COMPARE with effect of independent)

YES! shows independent variable causing result , not any other variable.

NO! experiment to determine whether result due to independent, nothing else

To conduct treat everything same but eliminate/replace independent used in experiment e.g. replace alcohol with H2O

%change/increase in mass/volume/ ratios: COMPARISON as initial diff

Analyse class results, student calculates % increase in pulse rate/student. YES: result comparison (as resting pulse maybe diff so accounting all results); NO: exercise not standardised so can't compare

RANDOM TESTING

Divide into 2 equal groups

keep control & experimental group 'same' for 1 factor e.g. age, sex, mass

Or divide randomly

which avoid bias/allows statistical analysis

STANDARD DEVIATION

BARS suggest about difference..?

WHAT it shows?

If SD bars don't overlap difference significant/more variation in one than the other

Overlapping SD results due to chance

SPREAD of measurements around mean/accounts all measurements

how reliable measurements are/mean is

Even without same sample size for each set of measurements, can calculate SD

ACCURACY

measuring time for larger volume drain using larger syringe: MORE ACCURATE as time to drain longer / less effect from stopping / starting timer / smaller percentage error;

Measuring pulse for shorter than 20 secs=>unreliable results. incomplete beats/cycles; Small difference in measurements can produce large difference in pulse rate when multiplied;

Length no shorter than instructed

using digital timer that measures to 0.0001 sec No/little difference) as effect of stopping / starting timer still has big effect

Judging when all solution has drained subjective / not as accurate as timer

Errors have relatively larger effect/length maybe not long enough to give measurable change

GRAPHS

Join points on graph straight lines NOT curve; no INTERMEDIATE values; can't predict rate between plotted values

Student said optimum pH for lactase was pH 6.0. Not valid as peak could be anywhere pH 5.5 - 7.5 / should've repeated experiment at appropriate pH

Should curve start from 0? NO: Curve shouldn't extend beyond data collected. YES at origin no product formation (in other cases control necessary to deduce this)

EXTRAPOLATE (extend curve)

ETHICS

Natural product used--safe i.e.no harmful effects;

No change to lifestyle of participants

Participants healthy, volunteers (own choice)

EVALUATING SUGGESTIONS/NEWSPAPERS

Newspaper: taking MCP will mean increased resistance to disease.

Farmer concluded from graph feeding cows on corn reduces omega-3 fatty acid content in milk. Evaluate conclusion

Conc not valid: response only observed in mice

Disease organisms not investigated

Not all disease caused by pathogens / cured by antibodies

The graph shows decrease with time feeding on corn (STATE TREND), No control group (-VE)/ may decrease with time than time spent feeding on corn (-VE)

Other named factor may've changed (other factors)

Only one investigation so might not be representative

PLACEBO & DRUG TRIALS

placebo juice used to dilute C juice--had same concentration of sugars, minerals & vitamins as C. P juice used instead of H2O...

To maintain constant intake of energy (Otherwise) result may've been due to diff amounts of sugars/minerals/vitamins

So that participants didn't know concentration of juice being used

EMPA: Common Themes