# Normal Distribution: sample mean, standard error, prob.

1. A population of unknown shape has a mean of 75. you select a sample of 40. the standard deviation of the sample is 5. What is the probability that the sample mean is between 76 and 77?

a. 0.3980

b. 0.8905

c. 0.0081

d. 0.3943

2. a population has a mean of 50 and a standard deviation of 12. FOr samples of size 9, sample mean and standard error of mean are?

a. 16.67 and 4

b. 50 and 1.33

c. 5.56 and 1.33

d. 50 and 4

3. A machine that fills soft drink cans underfill 20% of the. IF 15 cans are randomly inspected find the probability that no ore than two are underfilled?

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#### Solution Preview

1. A population of unknown shape has a mean of 75. you select a sample of 40. the standard deviation of the sample is 5. What is the probability that the sample mean is between 76 and 77?

a. 0.3980

b. 0.8905

c. 0.0081

d. 0.3943

Answer: 0.0973

(Please check your question; )

Mean=M = 75

Standard deviation =s= 5

sample size=n= 40

sx=standard error of mean=s/square root of n= 0.7906 = ( 5 ...

#### Solution Summary

Answers questions on Normal Distribution: sample mean, standard error of mean, probability.