Scientific Methods II
Peter Popper plants prodigious plots of pea plants.
Every week Peter measures the height of his pea plants and records the results.
LoggerPro Graph
Time
(weeks)
0
1
2
3
4
5
6
Height
(cm)
0
9.5
22.4
31.1
41.1
49.5
60.0
Scientific Methods II
Peter Popper plants prodigious plots of pea plants.
Every week Peter measures the height of his pea plants and records the results.
Since the graph is linear and
contains (0,0),
H t
The height is proportional
to the time
y

m
x  b
cm 
954cm
H  99..954
week



Every week the pea plant
grows on average 9.954 cm.
Scientific Methods II
Peter Popper plants prodigious plots of pea plants.
Every week Peter measures the height of his pea plants and records the results.
Since the graph is linear and
contains (0,0),
H t
y

m
H  9.954 cm
x  b

t
week
Scientific Methods II
Peter Popper plants prodigious plots of pea plants.
Every week Peter measures the height of his pea plants and records the results.
To determine whether or not the yintercept is significant:
Since the graph is linear and
contains (0,0),
1. Test of logic
y

H t
m
x  b
H  9.954 cm
What does it mean if there is a (0,0) point
on the graph?
At 0 weeks the height of the
pea plant is 0 cm.
week
t
Scientific Methods II
Peter Popper plants prodigious plots of pea plants.
Every week Peter measures the height of his pea plants and records the results.
To determine whether or not the yintercept is significant:
Since the graph is linear and
contains (0,0),
1. Test of logic
2. 5 % Rule – If the y-intercept is less then
5 % of the maximum y -value, it
can be considered negligible.
Maximum height (y-value) = 60 cm
5% 0f 60 cm = 0.05 x 60 cm
= 3.0 cm
3.0 cm > 0.6538 cm
Since the y-intercept is less than 5% of
the maximum y-value, it is negligible.
y

H t
m
x  b

H  9.954 cm week t