Biology Flashcards
(34 cards)
Why do you have controls in an experiment
to compare the results from an experiment to something else
to determine that any change in the DV is caused by changes to the IV.
how are the groups controlled
treated the same
drug administered the same
but given a dummy/fake drug/saline
what must you do to the variables
keep all the same to ensure an accurate result
whats the independent variable
thing you change x axis
whats the dependent variable
the thing you measure
y axis
whats a control variable
something you keep the same e.g sex age temperature
whats the use of percentages ratios rates
allows a comparison between two things that have different starting points e.g populations, starting masses, birth rates etc.
what is the link between correlation and causation on a graph
say if graph shows a positive or negative correlation
it may show a correlation doesn’t mean causation
could be due to another factor (give example)
state the points that don’t fit the pattern
what is bias
important to avoid so that everything is random
no professional or personal investment in the conclusion
random choice of sample/people so it is more representative
what do you do when it says evaluate
positives and negatives
say what data supports the conclusion
say what doesn’t support the conclusion
quote data
what do you do when it says describe
say what you see
quote figures
what do you do when it says explain
say why something has happened in detail with key terms and phrases
what do you do when it says suggest
give a sensible answer based on the info provided. no definitive answer
not been taught it specifically
use info to give sensible reason why
what is the use of a mean
allow comparison with different sample sizes
how do you find unknowns
say what variables you would plot
draw a line of best fit
state where you would extrapolate the answer on the graph
what is standard deviation
spread of data around the mean
check if they overlap
if they do no real difference between the results
if they don’t STILL MENTION
what to say about probability and chance
tells if theres a real or significant difference
there is a less than 5% probability the results are down to chance or there is a 95% prob the results aren’t down to chance
p means probability use a 0.05 or 0.01 most likely 0.05
what is uncertainty
every measurement has some kind of uncertainty
no smaller than plus or minus half of the smallest division
what to do with anomalous results
ignore them if they are one set of a repeated results
otherwise include to reduce the possibility that a key point is being overlooked
what is precision
little spread about the mean value
depends only on the extent of random errors
it gives no indication of how close results are to the true value
what does it mean for results to be repeatable
original experimenter repeats the investigation using the same method and equipment and gets the same results
what does it mean for results to be reproducible
if the investigation is repeated by another person or by using different equipment or techniques and the same result is achieved
how do you work out % change
change/original
x 100
how to calculate rate from a graph
draw a tangent to the curve or if its a straight line use that
pick two points on the line to give coordinates
y2-y1 divided by x2-x1 = rate
