isa variables
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ISA
The nature and type of variables in investigation skills assessments.
10 April 2023
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
A student obtained these results while doing an investigation to determine the possible link between the number of primary and secondary turns and the output voltage and power output of a transformer.
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
What type of variable is shown in this
column?
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
Independent variable
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
What is the natureof the variable is shown in this
column?
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
This is a discrete variable –
(whole number of turns)
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
What type of variable
is shown in this column?
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
Independentvariable – also discrete (whole
numbers of turns.)
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
What typeof
variableis shownin this
column?
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
Independentvariable,
This one is continuous(can take
any value).
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
What type of variable
is shown in this column?
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
Dependent variable – this
one is continuous –
can take any value.
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
What type of variable
is shown in this column?
Primary turnsSecondary
turnsPrimary voltage
Secondary voltage
Lamp brightness
120 240 4.0 8.0 bright
240 120 4.0 2.0 dull
60 120 4.0 8.0 bright
60 240 4.0 16.0 very bright
120 60 4.0 2.0 dull
300 600 4.0 8.0 bright
300 1200 4.0 16.0 very bright
Dependent variable – this
one is a categoric variable– its value is
described inwords.
Tray position pHAverage
height after 10 days
Colour of leaves after
10 days
On window of laboratory.
7 12.3cm Green
On window of laboratory.
5 9.2cm Green
On window of laboratory.
3 6.34cmGreen/ yellow
On window of laboratory.
1 1.23cmYellow -
dead
A student obtained these results while doing an investigation to determine the possible link between the pH (acidity) of water used on germinating cress seeds and their growth and colour.
Tray position pHAverage
height after 10 days
Colour of leaves after
10 days
On window of laboratory.
7 12.3cm Green
On window of laboratory.
5 9.2cm Green
On window of laboratory.
3 6.34cmGreen/ yellow
On window of laboratory.
1 1.23cmYellow -
dead
What type of variable is shown in this
column?
Tray position pHAverage
height after 10 days
Colour of leaves after
10 days
On window of laboratory.
7 12.3cm Green
On window of laboratory.
5 9.2cm Green
On window of laboratory.
3 6.34cmGreen/ yellow
On window of laboratory.
1 1.23cmYellow -
dead
This is a control variable
– to ensure this is a fair test.
Tray position pHAverage
height after 10 days
Colour of leaves after
10 days
On window of laboratory.
7 12.3cm Green
On window of laboratory.
5 9.2cm Green
On window of laboratory.
3 6.34cmGreen/ yellow
On window of laboratory.
1 1.23cmYellow -
dead
What type of variable is shown
in this column?
Tray position pHAverage
height after 10 days
Colour of leaves after
10 days
On window of laboratory.
7 12.3cm Green
On window of laboratory.
5 9.2cm Green
On window of laboratory.
3 6.34cmGreen/ yellow
On window of laboratory.
1 1.23cmYellow -
dead
This is anindependentvariable – it is also
a continuous
variable
Tray position pHAverage
height after 10 days
Colour of leaves after
10 days
On window of laboratory.
7 12.3cm Green
On window of laboratory.
5 9.2cm Green
On window of laboratory.
3 6.34cmGreen/ yellow
On window of laboratory.
1 1.23cmYellow -
dead
What type of variable
is shown in this column?
Tray position pHAverage
height after 10 days
Colour of leaves after
10 days
On window of laboratory.
7 12.3cm Green
On window of laboratory.
5 9.2cm Green
On window of laboratory.
3 6.34cmGreen/ yellow
On window of laboratory.
1 1.23cmYellow -
dead
This is a dependent
variable – it is also a continuous
variable.
Tray position pHAverage
height after 10 days
Colour of leaves after
10 days
On window of laboratory.
7 12.3cm Green
On window of laboratory.
5 9.2cm Green
On window of laboratory.
3 6.34cmGreen/ yellow
On window of laboratory.
1 1.23cmYellow -
dead
What type of variable
is shown in this column?
Tray position pHAverage
height after 10 days
Colour of leaves after
10 days
On window of laboratory.
7 12.3cm Green
On window of laboratory.
5 9.2cm Green
On window of laboratory.
3 6.34cmGreen/ yellow
On window of laboratory.
1 1.23cmYellow -
dead
This is a dependent variable
– it is also a category variable.
Group % CementForce (1)
(N)Force (2)
(N)Force (3)
(N)Ave Force (N)
1 20 45 50 40 45.0
2 30 60 70 50 60.0
3 40 90 80 90 86.7
4 50 120 130 120 123.3
5 60 150 140 160 150.0
Group % CementForce (1)
(N)Force (2)
(N)Force (3)
(N)Ave Force (N)
1 20 45 50 40 45.0
2 30 60 70 50 60.0
3 40 90 80 90 86.7
4 50 120 130 120 123.3
5 60 150 140 160 150.0
Group % CementForce (1)
(N)Force (2)
(N)Force (3)
(N)Ave Force (N)
1 20 45 50 40 45.0
2 30 60 70 50 60.0
3 40 90 80 90 86.7
4 50 120 130 120 123.3
5 60 150 140 160 150.0
A student obtained these results while doing an investigation to determine the strength of a concrete block as the percentage cement in the mix varies.
Group % CementForce (1)
(N)Force (2)
(N)Force (3)
(N)Ave Force (N)
1 20 45 50 40 45.0
2 30 60 70 50 60.0
3 40 90 80 90 86.7
4 50 120 130 120 123.3
5 60 150 140 160 150.0
What type of variable is shown
in this column?
Group % CementForce (1)
(N)Force (2)
(N)Force (3)
(N)Ave Force (N)
1 20 45 50 40 45.0
2 30 60 70 50 60.0
3 40 90 80 90 86.7
4 50 120 130 120 123.3
5 60 150 140 160 150.0
Independent variable –This is also
a continuousvariable – any value
of cement could be taken
Group % CementForce (1)
(N)Force (2)
(N)Force (3)
(N)Ave Force (N)
1 20 45 50 40 45.0
2 30 60 70 50 60.0
3 40 90 80 90 86.7
4 50 120 130 120 123.3
5 60 150 140 160 150.0
What type of variable is shown
in this column?
Group % CementForce (1)
(N)Force (2)
(N)Force (3)
(N)Ave Force (N)
1 20 45 50 40 45.0
2 30 60 70 50 60.0
3 40 90 80 90 86.7
4 50 120 130 120 123.3
5 60 150 140 160 150.0
Dependent variable –
The value is discrete becauseonly multiples
of 10N were available
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