The average lifetime of a light bulb is 3,000 hours with a ...

[azncindy619]

The average lifetime of a light bulb is 3,000 hours with a standard deviation of 696 hours. A simple random sample of 36 bulbs is taken.
 a. What are the expected value, standard deviation, and shape of the sampling distribution of ?
  b. What is the random variable in this problem? Define it in words.
  c. What is the probability that the average life in the sample will be between 2,670.56 and 2,809.76 hours?
 d. What is the probability that the average life in the sample will be greater than 3,219.24 hours?
  e. What is the probability that the average life in the sample will be less than 3,180.96 hours?

Question 2

The mean of a standard normal probability distribution _____.
 a. is always equal to 1
  b. can be any value as long as it is positive
  c. can be any value
  d. None of the answers is correct.

[ong527]

Answer to Question 1

a. 3,000; 116; normal
b. x, the average life in a sample of 36 bulbs
c. .0482
d. .0294
e. .9406

Answer to Question 2

d