# Mean

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I.) The number of construction projects on a college campus follows Poissan's dist. with a mean=3. The probability that exactly two projects are currently taking place is:

1.) 0.4230

2.) 0.224

3.) 0.00

4.) 0.1990

J.) In an assembly line with robots, a particular component can be installed in 90 seconds if holes are properly drilled and 12 minutes if holes have to be redrilled. 20 of the components are in stock and it's assumed that 2 will have improperly drilled holes. 5 of the components are selected at random from the 20. What is the probability that all 5 components will fit properly?

1.) 0.1

2.) 0.5526

3.) 0.4

4.) 0.0250

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##### Solution Summary

I.) The number of construction projects on a college campus follows Poissan's dist. with a mean=3. The probability that exactly two projects are currently taking place is:

1.) 0.4230

2.) 0.224

3.) 0.00

4.) 0.1990

J.) In an assembly line with robots, a particular component can be installed in 90 seconds if holes are properly drilled and 12 minutes if holes have to be redrilled. 20 of the components are in stock and it's assumed that 2 will have improperly drilled holes. 5 of the components are selected at random from the 20. What is the probability that all 5 components will fit properly?

1.) 0.1

2.) 0.5526

3.) 0.4

4.) 0.0250

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Probability Problems

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Two separate problems with multiple choice answers:

I.) The number of construction projects on a college campus follows Poissan's dist. with a mean=3. The probability that exactly two projects are currently ...

###### Education

- BSc , Wuhan Univ. China
- MA, Shandong Univ.

###### Recent Feedback

- "Your solution, looks excellent. I recognize things from previous chapters. I have seen the standard deviation formula you used to get 5.154. I do understand the Central Limit Theorem needs the sample size (n) to be greater than 30, we have 100. I do understand the sample mean(s) of the population will follow a normal distribution, and that CLT states the sample mean of population is the population (mean), we have 143.74. But when and WHY do we use the standard deviation formula where you got 5.154. WHEN & Why use standard deviation of the sample mean. I don't understand, why don't we simply use the "100" I understand that standard deviation is the square root of variance. I do understand that the variance is the square of the differences of each sample data value minus the mean. But somehow, why not use 100, why use standard deviation of sample mean? Please help explain."
- "excellent work"
- "Thank you so much for all of your help!!! I will be posting another assignment. Please let me know (once posted), if the credits I'm offering is enough or you ! Thanks again!"
- "Thank you"
- "Thank you very much for your valuable time and assistance!"

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