Good Science Victorian Curriculum Year 7

SCIENCE SKILLS
1.3
COLLECTING
AND USING DATA
KEY TERMS
inference
an educated guess or judgement
based on observations
observation
something you see and know to
be true
prediction
a statement about the future
based on observation and
evidence
primary data
first-hand data, from your own
investigation
qualitative
written descriptions and
observations
quantitative
numerical information and data
secondary data
second-hand data, from
someone else
CALCULATING
THE MEAN
To calculate the mean (also
known as the average) of a
group of numbers, add all the
numbers together and then
divide them by how many
numbers you added together.
For example, to calculate the
average growth of plant 3 in the
investigation about plants and
sunlight (Table 1), you would add
2, 3 and 5, then divide by 3.
The mean would be
(2 + 3 + 5) ÷ 3 = 3.33mm.
1
2
Data is like evidence – you need it to draw your conclusion.
Scientists collect and analyse data to test their hypotheses.
Scientists collect different types of data
One way to describe data is that it can be qualitative or quantitative.
Quantitative data relates to quantities – that is, numbers. Quantitative
data can include the number of something, the volume, the length, time,
or anything that scientists can physically measure or count. Qualitative
data relates to the qualities of something – that is, written descriptions
or observations about data.
Another way to describe data is as primary data or secondary data.
Primary data is first-hand data that you collect yourself through
scientific investigation. Secondary data is second-hand data,
gathered by someone else and given to or accessed by you.
To make sure secondary data is valid and reliable (see lesson 1.4),
you need to check that it comes from a reliable source. It’s also
important to make sure the data is accurate. If it is a survey, was the
sample size large enough or did it only involve a small number of
people? Are the results from just one country or population group?
How are qualitative and quantitative data different?
Data needs to be carefully collected
and recorded
To ensure that their data is valid, scientists record observations and
measurements very carefully. They might do this in a logbook or table
for quantitative data. Qualitative data might be recorded in a journal or
workbook. Sometimes data is visual and can be recorded with a camera.
When taking measurements and recording quantitative data, use
the appropriate units for physical quantities. This table shows some
common metric units for physical quantities.
Physical quantity Measurement and unit Conversion
Length Millimetre (mm) 10 mm = 1 cm
Centimetre (cm)
100 cm = 1 m
Metre (m)
1000 m = 1 km
Kilometre (km)
Mass Milligram (mg) 1000 mg = 1 g
Gram (g)
1000 g = 1 kg
Kilogram (kg)
Volume Millilitre (mL) 1000 mL = 1 L
Litre (L)
Temperature
Celsius (°C)
Why is it important to use the correct units when measuring?
8 GOOD SCIENCE VICTORIAN CURRICULUM 7