In a weight training class the mean
average weight for the bench press is 230 lbs. with a standard deviation of 5 lbs. If 10
students are chosen at random, determine the standard error.

A
mobile phone company determined with 95% confidence that the a teenager with a mobile phone send an
average of 180 text messages ± 20 messages each day.

Which of the following statement is
most likely to be true based on the study?

a.

There is a 95% probability that every student with a mobile phone sends at least 160
messages a day.

b.

There is a 95% probability that every student with a mobile phone sends at most 200
messages a day.

c.

There is a 95% probability that the true average of text messages sent by a teenager
is somewhere between 160 and 200 text messages a day.

d.

There is a 95% probability that the true
average of text messages sent by a teenager is 180 text messages a
day.

An
airline is trying to calculate an expected amount of baggage weight per passenger to predict fuel
expenses. Using a relatively large sample the airline determined that the sample mean for each
passenger was 34 pounds of luggage with a standard error of 4 pounds,
. Construct a 99% confidence interval that would describe the actual true average
weight of a passenger’s luggage weight.

a.

With 99 % confidence the true average weight of a passenger’s luggage is
between 30 and 38 pounds.

b.

With 99 % confidence the true average
weight of a passenger’s luggage is between 27.42 and 40.58
pounds.

c.

With 99 % confidence the true average weight of a passenger’s luggage is
between 26.16 and 41.84 pounds.

d.

With 99 % confidence the true average
weight of a passenger’s luggage is between 23.7 and 44.3
pounds.

A printer cartridge company claims their ink lasts for more than 5,000
words. The number of words printed is normally distributed with a standard deviation of 20
()

A
sample was taken of 50 cartridges and it was found that they had a mean of 4,940 words. Construct a
95% confidence interval (z = 1.96).

Using the interval does the company’s claim hold
true?

a.

No, the companies claims are above the 95% confidence interval.

c.

No, the companies
claims are below the 95% confidence interval.

b.

Yes, the companies claims fall within the 95%
confidence interval.

d.

Yes,
the companies claims are below the 95% confidence interval.

The store Better Buys knows that the
cost to repair a computer is normally distributed with a standard deviation of $40 ().

A random sample of 10 computer repairs and found the average of those 10 computer repairs was
$154. Construct a 95% confidence interval of the population mean of a computer repair.

An
admissions director wants to estimate the mean age of all students enrolled at a college. The
estimate must be within 1 year. The ages are not normally distributed so the director knows she will
need a sample of at least 30.

Determine the minimum required sample size to construct a 99%
confidence interval for the population mean. Assume the population standard deviation is 4.8
years ().