U3AOS1: scientific skills Flashcards
define aim
purpose/objective of an experiment
usually starts with ‘to determine’ or ‘to investigate’
define independent variable
the variable that is deliberately manipulated or changed by the experimenter -> should be only one variable to increase validity of data collected
define dependent variable
variable that is measured by experimenter to determine if change in IV had any effect
define controlled variable
variables that remain constant throughout the experiment -> important b/c ensure they don’t impact the validity of the data collected in the experiment
define hypothesis
a testable statement which predicts the outcome of an experiment/investigation
hypothesis formula
if the dv…. [phrase outline r’ship between dv and iv] … then … [trend indicating effect on the dv] … when … [trend indicating action by the iv]
define quantitative
analysis - identifies the amount of a substance present
data - provides a numerical value
define qualitative
analysis - technique that determines the composition of the sample
data - descriptive data collected based on observations
what is a systematic error
a consistent error which causes measured values to be skewed by a consistent amount every time -> affects accuracy eg. uncalibrated equip, parallax error
how to manage systematic errors
-measuring apparatus used should be calibrated prior to experiment
-change the experiment eg. using a quality primary standard
what is a random error
-unpredictable variations resulting in a spread of measurements
-differs in amount/proportion each time bc ‘one-off’ error
-affect precision
-eg. subjective judgements made/estimate measurement that falls between lines of burette
how to manage random errors
effect minimised by repeating measurements multiple times -> increased reliability, and calculate average of the results obtained, omit outliers
what is a personal error
results of mistakes made by the experimenter when misinterpret information eg. miscalculations, misreading scales
how to manage personal errors
repeating the experiment in the correct manner -> they are avoidable errors
define reliability + how to improve
refers to whether or not consistent results can be achieved when conducting the same experiment under varying conditions
improved by repeating experiment + averaging results
define repeatability + how to improve
how close measured values are from repeated experiments conducted using the same method, under the same measuring conditions by the same experimenter
improved by the use of precise equipment and ^ no. of measurements taken
define reproducibility + how to improve
describes the closeness of values measured from repeated experiments under different conditions eg. changes in equipment, environment, experimenter but ^ chance of random errors with more changes
improved by use of precise apparatus and increasing no. of measures
define validity
the extent to which an experiment investigates what it aims or claims to. results can answer aim/hypothesis. this is affected by both experimental design (eg controlled variables) and how it is conducted (eg observer bias).
internal = experimenter did everything right
external = confounding factors?
define accuracy
how close a measured value is to the true value of the quantity being measured
define precision
how closely two or more measurement values are in agreement with each other
define resolution
the smallest change in the quantity being measured that results in a perceptible change on the measuring instrument. eg. the resolution of a burette is 0.05 mL
define outliers
data points or observations that differ significantly from other data points or observations -> caused by mistakes so should be omitted, but must be accounted for before omission as an ethical approach to dealing with data
suggest why experiments are repeated
-to minimise impacts of random errors by taking on an average of the results obtained
-allows for experimenter to check that method is reliable/reproducible
what should you always link reliability to?
repeating experiment
