ISYE 6402 Official Midterm 1 MC | Questions and
Answers - Spring 2026 | 100% Correct - GT.
ISYE 6402 Time Series Analysis: Midterm 1 Practice Questions
Ans
Correct
wer
Question Answer &
Opti
Rationale
ons
B. False
Rationale:
While constant
mean is a
necessary
condition for
stationarity,
A. non-constant
Q1. If the mean of a time
True variance or
series does not depend on
B. significant
time t, then the time series is
Fals autocorrelation
stationary.
e may still be
present.
Stationarity
requires
constant mean,
constant
variance, and
autocovariance
, Ans
Correct
wer
Question Answer &
Opti
Rationale
ons
that depends
only on lag .
A. True
Rationale: The
variance of a
Q2. For a random walk process random walk
S<sub>t</sub> = A. increases with
Σ<sup>t</sup><sub>j=1</sub> True time.
X<sub>j</sub> where B. Var(S<sub>t</s
X<sub>t</sub> ∼ IID(0,σ²), we Fals ub>) = tσ²,
have that Var(S<sub>t</sub>) e which is greater
> Var(S<sub>t-1</sub>). than
Var(S<sub>t-
1</sub>) = (t-
1)σ² .
B. False
Rationale:
White noise
A. processes have
Q3. Consecutive observations True uncorrelated
in a white noise process are B. observations,
independent. Fals but
e uncorrelated
does not
necessarily
mean
, Ans
Correct
wer
Question Answer &
Opti
Rationale
ons
independent
unless the
process is
Gaussian.
Independence
is a stronger
condition .
<1
(abso
lute
value
less
than
1),
Q4. The AR(1) process is causal A. B. False not
if and only if the True Rationale: just
autoregressive parameter φ is B. The AR(1) φ betw
between 0 and 1. However, it Fals process is een 0
is always invertible. e causal if and
1.
The
condi
tion
requi
res
the
root
Answers - Spring 2026 | 100% Correct - GT.
ISYE 6402 Time Series Analysis: Midterm 1 Practice Questions
Ans
Correct
wer
Question Answer &
Opti
Rationale
ons
B. False
Rationale:
While constant
mean is a
necessary
condition for
stationarity,
A. non-constant
Q1. If the mean of a time
True variance or
series does not depend on
B. significant
time t, then the time series is
Fals autocorrelation
stationary.
e may still be
present.
Stationarity
requires
constant mean,
constant
variance, and
autocovariance
, Ans
Correct
wer
Question Answer &
Opti
Rationale
ons
that depends
only on lag .
A. True
Rationale: The
variance of a
Q2. For a random walk process random walk
S<sub>t</sub> = A. increases with
Σ<sup>t</sup><sub>j=1</sub> True time.
X<sub>j</sub> where B. Var(S<sub>t</s
X<sub>t</sub> ∼ IID(0,σ²), we Fals ub>) = tσ²,
have that Var(S<sub>t</sub>) e which is greater
> Var(S<sub>t-1</sub>). than
Var(S<sub>t-
1</sub>) = (t-
1)σ² .
B. False
Rationale:
White noise
A. processes have
Q3. Consecutive observations True uncorrelated
in a white noise process are B. observations,
independent. Fals but
e uncorrelated
does not
necessarily
mean
, Ans
Correct
wer
Question Answer &
Opti
Rationale
ons
independent
unless the
process is
Gaussian.
Independence
is a stronger
condition .
<1
(abso
lute
value
less
than
1),
Q4. The AR(1) process is causal A. B. False not
if and only if the True Rationale: just
autoregressive parameter φ is B. The AR(1) φ betw
between 0 and 1. However, it Fals process is een 0
is always invertible. e causal if and
1.
The
condi
tion
requi
res
the
root
