An auto dealer offers discounts averaging $2450 with a standard deviation of $575. If 50 autos are sold during one month, what is the expected value and standard deviation for the total discounts given?
E(total) = $122,500 SD(total) = $4,066
An auto dealer pays an average of $8750 with a standard deviation of $1200 for used car trade-ins, and sell new cars for an average of $28500 with a standard deviation of $3100. Assuming independence of trade-ins and new car prices for a customer, what is
root( (3100)^2 + (1200)^2) dollars
Suppose a retailer knows that the mean number of broken eggs per carton is 0.3 with a standard deviation of 0.18. In a shipment of 100 cartons, what is the expected number of broken eggs and what is the standard deviation? Assume independence between cart
E(broken) = 30 SD(broken) = 1.8
Science majors in college pay an average of $650 per year for books with a standard deviation of $130, whereas English majors pay an average of $465 per year for books with a standard deviation of $90. What is the mean difference and standard deviation be
E(diff) = $185 SD(diff) = $158
The auditor working for a veterinary clinic calculates that the mean annual cost of medical care for dogs is $98 with a standard deviation of $25 and that the mean annual cost of medical care for pets is $212 with an average deviation of $39 for owners wh
E(cats) = $114 SD(cats) = $30
A home theater projector system technician knows that based on past experiences, for unpacking, assembly, and fine tuning, the mean total setup time is 5.6 hours with a standard deviation of 0.886 hours. The times for the three steps are independent, the
E(fine tuning) = 1.3hr SD(fine tuning) = 0.15hr
Boxes of 50 "donut holes" weigh an average of 16.0 ounces with a standard deviation of 0.245 ounces. If the empty boxes alone weigh an average of 1.0 ounces with a standard deviation of 0.2 ounces, what are the mean and standard deviation of donut hole we
E(donut hole) = 0.3 oz SD(donut hole) = 0.02 oz
Which of the following is a true statement?
The area under a normal curve is always equal to 1, no matter what the mean and standard deviation are.
Which of the following is a true statement?
The are under the standard normal curve between 0 and 2 is half the area between -2 and 2
Populations P1 and P2 are normally distributed and have identical means. However, the standard deviation of P1 is twice the standard deviation of P2. What can be said about the percentage of observation falling within two standard deviations of the mean f
The percentage are identical
Which has the larger mean and which has the largest standard deviation?
Larger mean, b; larger standard deviation, a
A trucking firm determines that its fleet of trucks averages a mean of 12.4 miles per gallon with a standard deviation of 1.2 miles per gallon on cross-country hauls. What is the probability that one of the trucks averages fewer than 10 miles per gallon?
0.0228
A factory dumps an average of 2.43 tons of pollutants into a river every week. If the standard deviation is 0.88 tons, what is the probability that in a week more than 3 tons are dumped?
P(z > (3-2.43)/0.88)
An electronic product takes an average of 3.4 hours to move through an assembly line. If the standard deviation is 0.5 hour, what is the probability that an item will take between 3 and 4 hours?
0.6730
The mean score on a college placement exam is 500 with a standard deviation of 100. Ninety-five percent of the test takers score above what?
336
The average noise level in a restaurant is 30 decibels with a standard deviation of 4 decibels. Ninety five percent of the time it is below what value?
30 + 2.326(4)
The mean income per household in a certain state is $9500 with a standard deviation of $1750. The middle 95% of incomes are between what two values?
$6070 and $12,930
One company produces movie trailers with mean 150 seconds and standard deviation 40 seconds, while a second company produce trailers with mean 120 seconds and standard deviation 30 seconds. What is the probability that two randomly selected trailers, one
P(z < (180-270)/50)
Jay Olshansky from the University of Chicago was quoted in Chance News are arguing that for the average life expectancy to reach 100, 18% of people would have to live to 120. What standard deviation is he assuming for this statement to make sense?
21.7
Cucumbers grown on a certain farm have weights with a standard deviation of 2 ounces. What is the mean weight if 85% of the cucumbers weigh less than 16 ounces?
13.92
If 75% of all families spend more than $75 weekly for food, while 15% spend more than $150, what is the mean weekly expenditure and what is the standard deviation?
Mu (mean) = 104.39, standard deviation = 43.86
A coffee machine can be adjusted to deliver any fixed number of ounces of coffee. If the machine has a standard deviation in delivery equal to 0.4 ounces, what should be the mean setting so that an 8-ounce cup will overflow only 0.5% of the time?
6.97 ounces
Assume that a baseball team has an average pitcher, that is, one whose probability of winning any decision is 0.5. If this pitcher has 30 decisions in a season, what is the probability that he will win at least 20 games?
0.0505
Given that 10% of the nails made using a certain manufacturing process have a length less than 2.48 inches, while 5% have a length greater than 2.54 inches, what are the mean and standard deviation of the length of the nails? Assume that the lengths have
Mu (mean) = 2.506, standard deviation = 0.0205
Which of the following is a true statement?
Provided that the population size is significantly greater than the sample size, the spread of the sampling distribution does not depend on the population size
Which of the following is an incorrect statement?
The larger the value of the sample size n, the closer the standard deviation of the sampling distribution of x(bar) is to the standard deviation of the population
Which of the following is a true statement?
The sampling distribution of p(hat) has a mean equal to the population proportion of p
In a school of 2500 students, the students in an AP Statistics class are planning a random survey of 100 students to estimate the proportion who would rather drop lacrosse rather than band during this time of severe budget cuts. Their teacher suggests ins
reduce variability
The distribution of ages of people who died last year in the United States is skewed left. What happens to the sampling distribution of sample means as the sample size goes from n=50 to n=200?
The mean stays the same, the standard deviation becomes smaller, and the shape becomes closer to normal
Which of the following is the best reason that the sample maximum is not used as an estimator for the population maximum?
The sample maximum is biased
Which of the following are unbiased estimators for the corresponding population parameters?
All are unbiased
Thirty-four percent of Americans say that math is the most important subject in school. In a random sample of 400 Americans , what is the probability that between 30% and 35% will say that math is the most important subject?
0.618
Researchers found that in the aftermath of the 2011 Fukushima nuclear disaster, 12% of the pale grass blue butterfly larvae developed mutations as adults. What is the probability that in a random sample of 300 of these butterfly larvae, more than 15% deve
P(z > (0.15 - 0.12)/(root((0.12)(0.88)/300))
Suppose using accelerometers in helmets, researchers determine that boys playing high school football absorb an average of 355 hits to the head with a standard deviation of 80 hits during a season (including both practices and games). What is the probabil
0.571
It is estimated that school CO2 levels average 1200ppm with a standard deviation of 300ppm. In a random sample of 30 schools, what is the probability that the mean CO2 level is more than 1000, a level at which some researchers feel will cause a drop in ac
P (z > (1000 - 1200)/ (300/root30))
Binge drinking is a serious problem, killing more than 1700 college students per year. Suppose the incidence of binge drinking is 43% and 37%, respectively, at two large universities. In a random sample of 75 students at the first school and 80 students a
0.245
Suppose "sleep-trained" babies (allowed to cry themselves to sleep) wake up an average of 1.2 times a night with a standard deviation of 0.3 times, while non trained babies wake up an average of 1.8 times a night with a standard deviation of 0.5 times. In
0.0519
Which of the following statements are true?
I and II
Which of the following statements about t-distributions are true?
I only
A study is to be performed to estimate the proportion of voters who believe the economy is "heading in the right direction." Which of the following pairs of sample size and population proportion p will result in the smallest variances for the sampling dis
n = 1000 and p = 0.1
A random sample of 50 high school girls has a mean of 287 Facebook friends with a standard deviation of 68 friends. An independent random sample of 50 high school boys has a mean of 165 Facebook friends with a standard deviation of 45 friends. What is the
root ((68^2+45^2)/50)
Ina recent study of fatal automobile crashes for drivers ages 21-24, 32% were legally drunk, while for drivers ages 25-34, 29% were legally drunk. A simulation is conducted in which a random sample of 400 drivers ages 21-24 and a random sample of 400 driv
chart of -0.06, 0.0, 0.06, 0.12