Working Scientifically Skills and Depth Study booklet

Validity (NESA)

An extent to which tests measure what was intended; an extent to which data, inferences and actions produced from tests and other processes are accurate.

Hypothesis (NESA)

A tentative explaination for an observed phenomenon, expressed as a precise and unambiguous statement that can be supported or refuted by investigation.

Reliability (NESA)

An extent to which repeated observations and/or measurements taken under identical circumstances will yield similar results.

length (SI units)

metre (m)

mass (SI units)

kilogram (kg)

time (SI units)

second (s)

electric current (SI units)

ampere (A)

thermodynamic temperature (SI units)

kelvin (K)

amount of substance (SI units)

mole (mol)

Light intensity (SI units)

candela (cd)

frequency (derived unit)

hertz (Hz)

• s^-1 in SI units

force (derived unit)

newton (N)

• kg m s^-2 in SI units

tabulating data

needs to be atleast 5 changes made to the independent variable

often raw data needs to be manipulated first

conclusion (NESA)

A judgement based on evidence

pico (p)

x10^-12

• e.g. 1pm

nano (n)

x10^-9

• e.g. 1ns

micro (μ)

x10^-6

• e.g. 1μg

milli (m)

x10^-3

• e.g. 1mm

centi (c )

x10^-2

• e.g. 1cm

kilo (k)

x10³

• e.g. 1km

mega (M)

x10⁶

• e.g. MΩ

giga (G)

x10⁹

• e.g. GW

Random errors

fluctuations (in either direction) in the measured data due to the limitations of the measuring device. They can be reduced by averaged a large number of observations

Systematic errors

the measurement always differs from the actual value in the same way, may be due to calibration error, a zero error, technique error due to experimenter, or due to another cause

Incomplete definition

• systematic or random

• e.g. two people measuring same string, getting diff results, due to diff tension held at etc.

• to minimise: carefully conside and specify the conditions that could affect your measurement

Failure to account for a factor

• Usually systematic

• Can be corrected by taking account for an error that wasn’t detected earlier

Environmental factors