FeaturesHow It WorksFor ParentsPricingContactLog inStart free — no credit card needed →

Mathematical Methods · Unit 3 · Discrete random variables · Bernoulli distributions

Use a Bernoulli random variable as a model for two-outcome situations.

Practise this objective

AI-marked practice questions tied to QCAA mark schemes for this exact LO. Free to start.

Start free practice

Practice questions for this objective

Full questions, answers and worked solutions unlock when you start a free practice session.

Question 1

A quality-control inspector tests computer chips by checking whether each chip passes or fails a voltage stress test. This process can be modelled using a Bernoulli random variable. If the probability that a chip passes the test is $0.92$, which of the following correctly describes the Bernoulli model for this situation?

Worked answer
🔒 Start free to see full answer
Question 2

A quality control inspector tests electronic components for defects. Historical data shows that 8% of components are defective. The inspector randomly selects one component and records whether it is defective or not. Let \(X = 1\) if the component is defective and \(X = 0\) if it is not defective. (a) Identify the probability distribution of \(X\) and state the value of the parameter. [1 mark] (b) Calculate \(E(X)\), the expected value of \(X\). [1 mark] (c) Calculate \(\text{Var}(X)\), the variance of \(X\), to 4 decimal places. [1 mark]

Worked answer
🔒 Start free to see full answer
Question 3

A medical trial tests a new pain relief treatment. The table below shows the number of patients who experienced relief after one dose. (a) Use the table data to estimate the probability \(p\) that a randomly selected patient experiences relief. (1 mark) (b) Define a Bernoulli random variable \(X\) to model whether a single patient experiences relief, using the probability from part (a). State the distribution of \(X\) and determine \(E(X)\). (2 marks) (c) Use the information from part (b) to calculate \(\text{Var}(X)\). (1 mark)

Worked answer
🔒 Start free to see full answer
Question 4

A medical screening test for a disease has a success rate (detecting the disease when present) of 0.92. For each person tested, let $X = 1$ if the test correctly identifies the disease and $X = 0$ if it fails to detect the disease. If 8 people with the disease are screened, which value represents the probability that exactly 6 tests are successful?

Worked answer
🔒 Start free to see full answer
Question 5

A quality control inspector tests electronic components. Each component has a probability of $0.92$ of passing inspection. Let $X$ be a Bernoulli random variable where $X = 1$ if a component passes and $X = 0$ if it fails. (a) Determine $P(X = 1)$ and $P(X = 0)$. [1 mark] (b) Calculate the expected value $E(X)$ and variance $\text{Var}(X)$ for this Bernoulli random variable. [2 marks]

Worked answer
🔒 Start free to see full answer
Unlock all 5 answers — free

More in Bernoulli distributions

← Previous
Model and solve problems that involve Bernoulli random variables and associated probabilities, with and without technology.
All LOs in Bernoulli distributionsBack to full Mathematical Methods syllabus