These questions dig into carry‑over decay, half‑life priors, and pitfalls in estimating persistence.
Baseline decay half‑life refers to time it takes for carry‑over effect to drop by ______ %.
50
1
25
100
Half‑life measures exponential decay of prior period influence on current sales.
Longer half‑life values increase modelled incremental lift for ______ media.
paid search
SEO title
flash sale
brand TV
Brand channels sustain memory longer; decay parameter spreads effect across weeks.
Gamma‑distributed priors bias half‑life towards shorter tails if shape parameter is ______.
=100
negative
>5
<1
Shape <1 skews distribution, discouraging unrealistically long persistence.
Estimating half‑life jointly with saturation requires strong priors to prevent ______.
macro drift
identifiability issues
cookie errors
creative bias
High correlation between decay and saturation parameters can produce unstable estimates.
Carry‑over for price promos often shows near‑zero half‑life because demand is ______.
delayed
static
pulled forward
hidden
Sales spike during promo but revert quickly, leaving little persistence.
Robyn flags half‑life estimates >180 days as a warning for potential ______.
over‑fit
creative
multicollinearity
good fit
Such long tails rarely reflect reality and suggest model mis‑specification.
In LightweightMMM, decay input is expressed as retention rate λ where half‑life = ln(0.5)/ln(λ); λ close to 1 means ______ half‑life.
zero
short
negative
long
Retention near 1 implies slow decay, translating to large half‑life value.
Baselines with holiday spikes can confound decay estimation; analysts include holiday ______ to isolate persistent effects.
pixels
formats
dummies
cookies
Fixed effects absorb short, non‑persistent spikes, clarifying true decay behaviour.
Half‑life is applied after adstock transform for media but before ______ projection.
saturation curve
CPC bid
CPA calc
AMP
Adstocked signal then feeds into non‑linear saturation to model diminishing returns.
Decay parameter bounds generally restrict half‑life between 0 and ______ weeks.
104
1
26
260
A half‑year upper cap prevents implausible carry‑over while allowing generous memory for durable channels.
Starter
Review the basics.
Solid
Nice work—refine the details.
Expert!
Exceptional command of the topic.
