A population of 600 semiconductor wafers contains wafers from three lots. The wafers are categorized by lot and by whether they conform to a thickness specification, with the results shown in the following table. A wafer is chosen at random from the population. Write your answer as a fraction or a decimal, rounded to four decimal places.

Lot A- conforming: 80, nonconforming: 13
lot B- conforming: 170, nonconforming: 31
lot C- conforming: 265, nonconforming: 41
(a) What is the probability that the wafer is from Lot C?
(b) What is the probability that the wafer is nonconforming?

(c) What is the probability that the wafer is from Lot C and is nonconforming?

(d) Given that the wafer is from Lot C, what is the probability that it is nonconforming?

(e) Given that the wafer is nonconforming, what is the probability that it is from Lot C?

(f) Let Ev1 be the event that the wafer comes from Lot C, and let Ev2 be the event that the wafer is nonconforming. Are Ev1 and Ev2 independent?

User Icon for Bot GPT 4-o mini Bot GPT 4-o mini answered
yesterday

Let's first summarize the data presented in the problem.

Summary of Wafers:

| Lot | Conforming | Nonconforming | Total | |------|------------|---------------|--------| | A | 80 | 13 | 93 | | B | 170 | 31 | 201 | | C | 265 | 41 | 306 | | Total | 515 | 85 | 600 |

Calculations:

(a) What is the probability that the wafer is from Lot C?

The total number of wafers from Lot C is 306.

\[ P(\text{Lot C}) = \frac{\text{Number of wafers in Lot C}}{\text{Total number of wafers}} = \frac{306}{600} = 0.51 \]

Rounded to four decimal places:

\[ P(\text{Lot C}) = 0.5100 \]


(b) What is the probability that the wafer is nonconforming?

The total number of nonconforming wafers is 85.

\[ P(\text{Nonconforming}) = \frac{\text{Number of nonconforming wafers}}{\text{Total number of wafers}} = \frac{85}{600} \approx 0.1417 \]

Rounded to four decimal places:

\[ P(\text{Nonconforming}) = 0.1417 \]


(c) What is the probability that the wafer is from Lot C and is nonconforming?

The number of nonconforming wafers from Lot C is 41.

\[ P(\text{Lot C and Nonconforming}) = \frac{\text{Number of nonconforming wafers in Lot C}}{\text{Total number of wafers}} = \frac{41}{600} \approx 0.0683 \]

Rounded to four decimal places:

\[ P(\text{Lot C and Nonconforming}) = 0.0683 \]


(d) Given that the wafer is from Lot C, what is the probability that it is nonconforming?

Using conditional probability,

\[ P(\text{Nonconforming | Lot C}) = \frac{P(\text{Lot C and Nonconforming})}{P(\text{Lot C})} = \frac{41/600}{306/600} = \frac{41}{306} \approx 0.1346 \]

Rounded to four decimal places:

\[ P(\text{Nonconforming | Lot C}) = 0.1346 \]


(e) Given that the wafer is nonconforming, what is the probability that it is from Lot C?

Again using conditional probability,

\[ P(\text{Lot C | Nonconforming}) = \frac{P(\text{Lot C and Nonconforming})}{P(\text{Nonconforming})} = \frac{41/600}{85/600} = \frac{41}{85} \approx 0.4824 \]

Rounded to four decimal places:

\[ P(\text{Lot C | Nonconforming}) = 0.4824 \]


(f) Are Ev1 (wafer comes from Lot C) and Ev2 (wafer is nonconforming) independent?

To check for independence, we can see if

\[ P(\text{Lot C and Nonconforming}) = P(\text{Lot C}) \cdot P(\text{Nonconforming}) \]

Calculating:

\[ P(\text{Lot C}) \cdot P(\text{Nonconforming}) = 0.51 \times 0.1417 \approx 0.0723 \]

Since \( P(\text{Lot C and Nonconforming}) \approx 0.0683 \) is not equal to \( P(\text{Lot C}) \cdot P(\text{Nonconforming}) \approx 0.0723 \), the events are not independent.

Thus, we conclude that:

Ev1 and Ev2 are not independent.