Question

1. An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 50 hours. If a sample of 40 bulbs has an average life of 730 hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm. The confidence interval is: <μ<? 2. The heights of a random sample of 60 college students showed a mean of 184.6 centimeters and a standard deviation of 6.8 centimeters. (a) Construct a 98% confidence interval for the mean height of all college students. The confidence interval is: <μ<? (b) What can we assert with 98% confidence about the possible size of our error if we estimate the mean height of all college students to be 184.6 centimeters? 3. A random sample of 100 automobile owners in a region shows that an automobile is driven on average 24,000 kilometers per year with a standard deviation of 3100 kilometers. Assume the distribution of measurements to be approximately normal. (a) Construct a 90% confidence interval for the average number of kilometers an automobile is driven annually in the region. The confidence interval is: <μ<? (b) What can we assert with 90% confidence about the possible size of our error if we estimate the average number of kilometers driven by car owners in the region to be 24,000 kilometers per year?

          1. An electrical firm manufactures light bulbs that have a
length of life that is approximately normally distributed with a
standard deviation of 50 hours. If a sample of 40 bulbs has an
average life of 730 hours, find a 96% confidence interval for the
population mean of all bulbs produced by this firm. The
confidence interval is: ____<μ<____?
2. The heights of a random sample of 60 college
students showed a mean of 184.6 centimeters and a
standard deviation of 6.8 centimeters.
(a) Construct a 98% confidence interval for the mean
height of all college students. The confidence interval is:
____<μ<____?
(b) What can we assert with 98% confidence about the
possible size of our error if we estimate the mean height of all
college students to be 184.6 centimeters?
3. A random sample of 100 automobile owners in a
region shows that an automobile is driven on
average 24,000 kilometers per year with a standard
deviation of 3100 kilometers. Assume the distribution of
measurements to be approximately normal.
(a) Construct a 90% confidence interval for the
average number of kilometers an automobile is driven annually in
the region. The confidence interval is: ____<μ<____?
(b) What can we assert with 90% confidence about the
possible size of our error if we estimate the average number of
kilometers driven by car owners in the region to
be 24,000 kilometers per year?

Added by Eric W.

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