Discrete cumulative distribution functions

STA 112. Practice questions, not past papers.

Lessons

• Build a step distribution function
• Read probabilities from jumps

Practice questions

1. A CDF F(t) equals which probability?

   Statistics study edition practice item Q122; Source: S17-18; T49-50, T74-77

2. At a discrete point x, its probability mass equals what?

   Statistics study edition practice item Q123; Source: S17-18; T49-50, T74-77

3. Every CDF must be what?

   Statistics study edition practice item Q124; Source: S17-18; T49-50, T74-77

4. For any CDF, P(a<X≤b) equals what?

   Statistics study edition practice item Q125; Source: S17-18; T49-50, T74-77

5. X has masses 1/4,1/2,1/4 at -1,2,5. What is F(2)? Give the value to 4 decimal places.

   Statistics study edition practice item Q126; Source: S17-18

6. A CDF jumps from 1/6 to 1/2 at x=6. Find P(X=6). Give the value to 4 decimal places.

   Statistics study edition practice item Q127; Source: S18

7. X has masses 1/4,1/2,1/4 at -1,2,5. Find P(X>2). Give the value to 4 decimal places.

   Statistics study edition practice item Q128; Source: S17-18

8. A discrete CDF is right-_____ at its jumps.

   Statistics study edition practice item F041; Source: S17-18; T49-50, T74-77

9. The probability mass at x is the size of the CDF _____ there.

   Statistics study edition practice item F042; Source: S17-18; T49-50, T74-77

Topic gap report