Question 1
A factory produces bolts, with 8% being defective. A random sample of 25 bolts is selected. Let be the number of defective bolts. Which distribution correctly models ?No clue? Show me the answer
Correct answer
Correct!
IncorrectStep-by-step walkthrough
Choose a solution method
Method #1Worked solutionStep 1: Identify n and p
The number of trials is bolts, and the probability of success (defective) is .
Step 2: Apply binomial notation
Since trials are fixed, independent, with two outcomes and constant probability, with , .
Step 3: Write distribution
This gives .
Step 4: Select answer
The correct notation is , option A.
Method #2Why the others are wrongStep 1: Option B
Swaps and , giving 8 trials with probability 0.25 - incorrect order of parameters.
Step 2: Option C
Uses the probability of failure (0.92) instead of success (0.08) as .
Step 3: Option D
Reverses the order of parameters entirely, writing before , which is not standard notation.
Step 4: Conclusion
Only option A correctly assigns and in the correct order.
Question 2
Which of the following scenarios satisfies all four conditions required for a binomial distribution?No clue? Show me the answer
Correct answer
Correct!
IncorrectStep-by-step walkthrough
Choose a solution method
Method #1Worked solutionStep 1: Check each condition
A binomial setup needs fixed trials, two outcomes, constant probability, and independence.
Step 2: Test option B
Rolling a die 12 times: is fixed, success = 'rolled a 4', constant, rolls are independent.
Step 3: Confirm all conditions met
All four conditions hold, so this is a valid binomial scenario.
Step 4: Select answer
Option B is the correct binomial scenario.
Method #2Why the others are wrongStep 1: Option A
Sampling without replacement changes the probability of drawing a spade each time, violating constant probability.
Step 2: Option C
There is no fixed number of trials; the number of days is variable, not fixed.
Step 3: Option D
This is a 'trials until first success' scenario with no fixed , which follows a geometric distribution, not binomial.
Step 4: Conclusion
Only option B has a fixed , two outcomes, constant , and independence.