Every
spring
the
city
of
Nenana,
Alaska
hosts
a
contest
in
which
participants
try
to
guess
the
exact
minute
that
a
wooden
tripod
placed
on
the
frozen
Tanana
river
will
fall
through
the
breaking
ice.
The
contest
started
in
1917
as
a
diversion
for
railroad
engineers,
with
a
jackpot
of
$800
for
the
closest
guess.
It
has
grown
into
an
event
in
which
hundreds
of
thousands
of
entrants
submit
their
estimates
on
the
internet.
The
2021
prize
money
for
the
closest
guess
was
$233,591.
Because
so
much
money
and
interest
depends
on
the
time
of
ice
breakup,
it
has
been
recorded
to
the
nearest
minute
with
great
accuracy
ever
since
1917.
And
because
a
standard
measure
of
breakup
has
been
used
throughout
this
time,
the
data
are
consistent.
We
will
investigate
if
we
can use
the
past
data
to
make
a
good
prediction
of
the
next
breakup
time.
This
Excel
file
Nenana
Ice
Breakup
Times
shows
the
data
from
the
beginning
of
the
contest
through
2021.
To
acquire
some
understanding
of
the
data
you
should
make
a
scatterplot
of
the
data
with
"Year
(since
1900)"
on
the
x-axis
and
"Day
Number"
on
the
y-
axis.
Column
C
lists
the
ice
breakup
for
each
year
as
the
number
of
days
from
the
beginning
of
that
year
starting
with
January
1
as
day
1.
For
example,
the
breakup
in
1998
is
listed
as
109.7045
days
from
January
1,
1998.
Day
109
of
1998
is
April
19;
0.7045
days
is
an
additional
16.908
hours,
or
16
hours
and
54
minutes.
Therefore
the
breakup
in
1998
occurred
on
April
20,
4:54
PM.
As
another
example,
in
1992
(a
leap
year),
the
breakup
time
is
listed
as
134.2684.
Day
number
134
in
1992
is
May
13;
0.2684
days
is
an
additional
6.4416
hours,
or
6
hours
and
26
minutes.
Therefore
the
breakup
occurred
on
May
14,
6:26
AM.
Question
1.
Exclude
the
data
for
2021
and
find
the
slope
and
intercept
of
the
least
squares
line
using
"Year
(since
1900)"
as
the
predictor
variable
(x-variable)
and
"Day
Number"
as
the
response
variable
(y-variable).
-0.0863
«
slope
(use
4
decimal
places;
don't
forget
to
exclude
the
data
for
2021)
130.4990
«
intercept
(use
4
decimal
places;
don't
forget
to
exclude
the
data
for
2021)
Question
2.
Use
the
least
squares
line
to
predict
the
ice
breakup
time
in
2021.
O
April
20,
9:08
AM
O
May
2,
1:40
AM
O
April
20,
7:09
PM
@
April
30,
1:12
AM
O
May
1,
8:41
PM
O
April
25,
10:43
AM
O
May
5,
2:16
PM
v
