Discrete random variables — Question 124
Original QCE Vault practice · 4 marks
Q124 · Practice questionTechnology-freeSimple familiar4 marks
QUESTION 124 (4 marks)
For the discrete distribution P(X=0)=0.1, P(X=1)=0.2, P(X=2)=0.4 and P(X=3)=0.3, calculate the mean and standard deviation of X. WORKED SOLUTION
Practice marking scheme
4 marksANSWERE(X)=1.9 and σ=0.89≈0.943. Worked solution
E(X)=1.9 and E(X2)=4.5. Hence Var(X)=4.5−1.92=0.89, so σ=0.89≈0.943. Correctly calculates E(X). Correctly calculates the standard deviation.
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
View the QCAA syllabusHow many marks did you earn?Compare your working with the guide above.
Related questions
- Q5 · Original practice · 1 mark
A discrete random variable X has P(X=x)=k(x+1) for x=0,1,2. Determine k. - Q15 · Original practice · 1 mark
For a discrete random variable, P(X=0)=0.2, P(X=1)=0.5 and P(X=2)=0.3. Determine E(X). - Q25 · Original practice · 1 mark
Let X∼Bin(3,0.4). Determine P(X≥2∣X≥1), to three decimal places. - Q30 · Original practice · 3 marks
Let X∼Bin(5,0.3). Determine P(X=2) to four decimal places.