In a manufacturing plant, the probability of making a defective bolt i...
It’s a poission distribution. Here n = 900, p = 0.1
∴ mean (m)= np = 900 × 0.1 = 90
Standard deviat ion (σ)=
= √81 = 9 (∵ σ > 0).,
In a manufacturing plant, the probability of making a defective bolt i...
Problem:
In a manufacturing plant, the probability of making a defective bolt is 0.1. The mean and standard deviation of defective bolts in a total of 900 bolts are respectively
a) 90 and 9
b) 9 and 90
c) 0.9 and 90
d) 90 and 0.9
Solution:
To solve this problem, we need to understand the relationship between probability, mean, and standard deviation.
Mean:
The mean is the average value of a set of numbers. In this case, the mean represents the expected number of defective bolts out of the total 900 bolts.
Standard Deviation:
The standard deviation measures the amount of variation or dispersion in a set of numbers. In this case, the standard deviation represents the spread or variability in the number of defective bolts.
Probability:
The probability of making a defective bolt is given as 0.1, which means that out of every 10 bolts produced, one bolt is expected to be defective.
Calculating the Mean:
To calculate the mean, we multiply the total number of bolts by the probability of making a defective bolt.
Mean = Total Number of Bolts * Probability
Mean = 900 * 0.1
Mean = 90
Hence, the mean of defective bolts in a total of 900 bolts is 90.
Calculating the Standard Deviation:
To calculate the standard deviation, we use the formula:
Standard Deviation = Square Root of (Total Number of Bolts × Probability × (1 - Probability))
Standard Deviation = √(900 × 0.1 × (1 - 0.1))
Standard Deviation = √(900 × 0.1 × 0.9)
Standard Deviation = √(81)
Standard Deviation = 9
Hence, the standard deviation of defective bolts in a total of 900 bolts is 9.
Conclusion:
The mean and standard deviation of defective bolts in a total of 900 bolts are 90 and 9, respectively. Therefore, the correct answer is option A) 90 and 9.