Lemma
MediumContinuous distributions
OpenStax, Introductory Statistics 2e §5.3 The Exponential Distribution · Exercise 28 · Probability · Continuous distributions

The Exponential Distribution · Exercise 28

Suppose that the useful life of a particular car battery, measured in months, decays with parameter 0.025. We are interested in the life of the battery.

(a) Define the random variable. X = _________________________________.
(b) Is X continuous or discrete?
(c) X ~ ________
(d) On average, how long would you expect one car battery to last?
(e) On average, how long would you expect nine car batteries to last, if they are used one after another?
(f) Find the probability that a car battery lasts more than 36 months.
(g) Seventy percent of the batteries last at least how long?

~8 minWritten answer · check your work with Lemma

OpenStax, Introductory Statistics 2e · §5.3 The Exponential Distribution · Exercise 28

Stuck? A gentle nudge

No hints for this one.

Something off?
Workspace
Your working

Check your full solution

Attach photos of your pages (up to 3) or one PDF — or check what you typed above. Lemma reads the work and verifies the reasoning, not just the answer.

Your first check today doesn't need an account.

Your photos and PDFs are read once and not stored — only the transcription is kept.