Download Chapter 8 Review - Milan C-2

Chapter 8
Review
Large Sample
Small Sample
Binomial
Choosing Sample Size
• A random sample of 60 employees opf a
large corporation had a sample mean
x=32.5 accumulated vacation days with
sample standard deviation s=18.5 days.
Find a 90% confidence level for the
population mean number of accumulated
vacation days.
• A random sample of 50 calls initiated on
cellular phones had a mean duration of 3.5
minutes with standard deviation 1.2
minutes. Find a 99% confidence interval
for the population mean duration of
telephone calls initiated on cellular
phones.
• A random sample of ten jumbo burgers
from a local diner had the following
weights (in ounces.) If µ is the mean
weight of all jumbo burgers served at the
diner, find a 99% confidence interval for µ.
12.1 12.4 11.8 12.6 11.9
11.5 12.2 11.3 11.7 12.3
• In wine making, acidity of the grape is a
crucial factor. A pH range from 3.1 to 3.6
is considered very acceptable. A random
sample of 12 bunches of grapes was
taken from a California vineyard. The
sample mean acidity was 3.38 with sample
standard deviation 0.20. Find a 99%
confidence interval for the mean acidity of
the entire harvest of grapes from this
vineyard.
• A postmaster in a large city found that 56
packages out of a random sample of 400
packages had insufficient postage. Find a
99% confidence interval for the population
proportion of packages with insufficient
postage.
• A member of the House of Representatives
wants to determine the proportion of voters in
her district who favor a flat income tax. A
random sample of 200 voters in her district
showed 89 in favor. Let p represent the
proportion of voters who favor a flat income tax.
A) Find a point estimate for p
B) Find a 95% confidence interval for p
C) Does the data indicate whether a majority of
the voters oppose the tax? Explain.
• A seed company advertises that the mean
time from planting to harvest for a new
variety of zucchini seeds is 50 days. The
standard deviation is estimated to be 10.3
days. If we wanted to verify this claim how
large a sample would we need in order to
state with 95% confidence that our sample
mean differs from the population mean by
no more than 3 days?
• Union officials want to estimate the percent, p, of
workers in the Big Bend Metalworks who favor a
strike. The union wants to have 90% confidence
that its estimate for p is within 2.5% of the true
proportion of workers who favor a strike.
A) If no accurate estimate for p is available, how
large a sample of workers is necessary?
B) A preliminary sample of 100 workers gave
r/n=0.35. How many more workers should be
included in this sample?