EMPA: Common Themes - created from Mind Map

SAMPLE SIZE, REPEATS & ANOMALIES 2 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 diffAnalyse 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