Download Review for Chapter 7 The average weight of 40 randomly selected

Review for Chapter 7
1. The average weight of 40 randomly selected minivans was 4150 lbs. The
population standard deviation was 480 lbs. find a point estimate of the
population mean. Find the 99% confidence interval of the mean weight of the
minivans.
2. A student randomly surveyed 36 other students and found that the mean
amount spent for text books was $121.60. If the standard deviation of the
population was $6.36, find the best point estimate and the 90% confidence
interval of the true mean.
3. A researcher wishes to estimate within $300 the true average amount of
money a county spends on road repairs each year. If she wants to be 90%
confident, how large does the sample need to be? The standard deviation is
$900.
4. A survey of 90 randomly selected families showed that 40 owned at least one
television set. Find the 95% confidence interval of the proportion of families
who own at least one television set.
5. A nutritionist wishes to determine, within 3%, the true proportion of adults
who of not eat any lunch. If he wishes to be 90% confident that his estimate
contains the population proportion, how large a sample will be necessary? A
previous study found that 15% of the 125 surveyed said they did not eat
lunch.
6. A dean wishes to estimate the average number of hours students spend
studying per week. The standard deviation from a previous study is 2.6 hrs.
How large of sample must be selected if he wants to be 99% confident of
finding whether the true mean differs from the sample mean by .5 hours?
7. You wish to conduct a study to find the true proportion of people that eat
turkey on Thanksgiving. You wish to be with 4% of the true proportion with
95% confidence.
8. Using the data below, determine the point estimate of the average Christmas
tree height then construct a 90% confidence interval for the true average
Christmas tree height.
8
7.5
7.5
9
12
7
6
8
8
9
8
10
7
10.5
7.5
8
8
7
9. What happens when you increase the confidence interval from 95% to 99%?
Previous Chapters
1. The probability of winning on a slot machine is 5%. If a person plays the
machine 500 times, find the probability of winning 30 times. Use the normal
approximation to the binomial distribution.
2. In a large university, 30% of the incoming students elect to enroll in a
personal finance course offered by the university. Find the probability that of
800 randomly selected students, at least 260 have elected to enroll in the
course using the normal approximation to the binomial distribution.
3. The average number of mg of sodium in a frozen dinner is 660 mg, and the
standard deviation is 35mg. Assume the variable is normally distributed. If a
sample of 10 dinners is selected, find the probability that the mean of the
sample will be larger than 670mg.
4. If 3% of all cars fail the emissions inspection, find the probability that in a
sample of 90 cars, 3 will fail. Use the Poisson Distribution.
5. At a food bank a case of donated items contains 10 cans of sour, 8 cans of
vegetables, and 8 cans of fruit. Find the probability of getting 1 can of
vegetables and 2 cans of fruit if a total of 3 cans are selected.
6. The probability a caller to Dominoes orders Pepperoni pizza is 42%, sausage
pizza is 30% and all other pizzas 28%. If 20 pizzas are ordered, what is the
probability 10 are pepperoni 6 are sausage and 4 are other.
Answers for Review
1. 4150, 3954<𝝁<4346
2. $121.60, $119.85< 𝝁<$123.35
3. 25
4. .342<p<.547
5. 384
6. 180
7. 601
8. Point estimate = 8.22, 7.63 < µ < 8.81
9. You would get a wider interval and are more likely to have the mean in your
interval.
1.
2.
3.
4.
5.
6.
.0496
.0668
.1841
.2205
.086
.030