Tutors Answer Your Questions about Probability-and-statistics (FREE)
Question 612040: on a multiple choice test with 9 questions, each question has 4 possible answers, only one of which is correct. For students who guess at all answers, find the mean for the number of correct answers.
I understand that the probability of getting a correct answer is 1/4 or .25 (my instructor likes all work in decimals). so to get the mean is it .25^9? also wouldn't I have to know how many students took the test to find out how many got them correct? I really don't understand this problem.
Click here to see answer by jim_thompson5910(28715)  |
Question 612206: the probability that sam will finish his homework is 90% and the probability mark will finish his homework is 80%. If these events are independent, find the probability that both Mark and Sam will finish their homework on a randomly selected day?
Click here to see answer by stanbon(57966) |
Question 612264: A confidence interval estimate for the population mean is given to be (40.45, 49.24). If the standard deviation is 11.159 and the sample size is 35, answer each of the following (show all work):
(A) Determine the maximum error of the estimate, E.
(B) Determine the confidence level used for the given confidence interval.
Click here to see answer by stanbon(57966) |
Question 612254: A study was conducted to estimate the mean amount spent on birthday gifts for a typical family having two children. A sample of 130 was taken, and the mean amount spent was $182.29. Assuming a standard deviation equal to $45.23, find the 95% confidence interval for m, the mean for all such families (show all work).
Click here to see answer by stanbon(57966) |
Question 612175: Nine percent of adult males connot distinguish between the colors green and red. if samples of 10 men is taken.
A)what is the expected number of re/green colorbind men in the sample?
B( calcute the exact probability that 3 of the men will be red/green colorblind?
Click here to see answer by stanbon(57966) |
Question 612153: a sample of 85 golfers showed that their average score on a particular golfers course was 91.31 with a standard deviation of 5.37. show all work.
A) find the 99% confidence interval of the mean score for all 85 golfers.
B) find the 99% confidence interval of the mean score for all golfers if this is a sample of 120 golfers instead of a sample of 85.
C) which onfidence interval is smaller and why?
Click here to see answer by stanbon(57966) |
Question 612306: U.S. Bureau of the Census data reveal the town of Smallville, OH has a population of 10 families. These families own the following:
Family X1 X2 X3 X4 X5 X6 X7 X8 X9 X10
Autos 4 5 3 2 2 3 3 1 4 3
TVs 4 4 5 3 3 4 5 5 4 3
Using the Census data above, 28 of the TVs were made in America. If the local TV repair shop randomly selects 5 different TVs for inclusion in a production study, what is the probability of the following:
a. None of the TVs was made in America?
b. At least one of the TVs was made in America?
c. Six TVs were made in America?
Click here to see answer by jmesch94(1)  |
Question 612276: construct the probability distribution describing the experiment of rolling a pair of dice 3 times, and counting as x the number of time a total of 9 is rolled. then find the mean and standard deviation of the distribution.
Click here to see answer by stanbon(57966) |
Question 612405: a researcher is interested in estimating the noise levels in decibels at area urban hospitals. she wants to be 95% confident that her estimate is correct. If the standard deviation is 5.48, how large a sample is needed to get the desired information to be accurate within 0.68 decibels. show work please.
Click here to see answer by stanbon(57966) |
Question 612409: In april 2004 article on Hear the Issue.com stated that Americans have an average of 2.24 televisions per households. If the standard deviations for the number of televisions in a U.S household is 1.2 and a random sample of 80 American households is selected, the mean of this sample belongs to a sampling disributions.
What is the mean and standard deviation of this sampling distribution?
2. Assume that the population of heights of male college students is approximately normally distributed with the mean of 69.09 inches and standard deviation of 4.71 inches. A random sample of 92 heights is obtained.
A. Find the mean and standard error of the x distribution.
B. Find P(x>68.50)
Help is greatly appreciated.
Click here to see answer by stanbon(57966) |
Question 612394: The control department of a light bulb manufacturer randomly picks 4400 light bulbs from the production lot every week. The records show that, when there is no malfunction, the defect rate in the manufacturing process (due to imperfections in the material used) is 1% . When 1.25% or more of the light bulbs in the sample of 4400 are defective, the control unit calls repair technicians for service.
Find the mean of P , where P is the proportion of defective light bulbs in a sample of 4400 when there is no malfunction.
Find the standard deviation of P .
Compute an approximation for P(p>=0.0125) , which is the probability that the service technicians will be called even though the system is functioning properly. Round your answer to four decimal places.
Click here to see answer by stanbon(57966) |
Question 612428: U.S. Bureau of the Census data reveal the largest town in the State of OH has a population of one million families. The data show that acreage owned per family is normally distributed with a mean of 10.0 acres and a standard deviation of 1.5 acres. Calculate the following:
a. The percentage of families that own at least 8.1 acres.
b. The number of families that own at least 8.1 acres.
c. The percentage of families that own between 7.0 and 8.1 acres.
d. The minimum acreage owned by the 5% of families owning the largest amount of acreage.
e. If one family from the State of OH is selected at random, what is the probability that family owns more than 8.1 acres or less than 7.0 acres?
Click here to see answer by ewatrrr(10682)  |
Question 612552: Let R = {1,2,3} S= {3,4,5}, and U= {1,2,3,4,5,6,7,8} Determine
a) R U S
b) R inverse of a)
C) S'
Click here to see answer by solver91311(17077)  |
Question 612572: Please help me to answer this. I am as lost as I can be. I truly need you.
If an island’s only residents are penguins and
bears, and if there are 15 heads and 36 feet on the
island, how many penguins and how many bears
are on the island?
Click here to see answer by scott8148(6628)  |
Question 612572: Please help me to answer this. I am as lost as I can be. I truly need you.
If an island’s only residents are penguins and
bears, and if there are 15 heads and 36 feet on the
island, how many penguins and how many bears
are on the island?
Click here to see answer by stanbon(57966) |
Question 612520: if each coded item in catalog begins with 3 distinct letters followed by nonzero digits ,find the probability of randomly selecting one of these coded items with the first letter a vowel and the last digit even
Click here to see answer by stanbon(57966) |
Question 612518: Consider a low cost airline operating a 120-seat plane. The company typically sells 125 tickets on the flight since not all passengers usually show up for their reserved seat.
The probability that a passenger misses his/her flight is 0.10 and we consider that all passengers behave independently.
(a) What is the probability that every passenger who shows up for the flight can get a seat?
Click here to see answer by stanbon(57966) |
Question 612468: An averages of four tax evaders per 100 tax filers. If 50 tax filers are randomly selected from the state, what is the probability of the following:
a. Exactly one tax filer will be a tax evader?
b. At most three filers will be tax evaders?
c. Over nine filers will be tax evaders?
Click here to see answer by stanbon(57966) |
Question 612660: assume that a sample is drawn and z(a/2)= 1.96 AND 0=25. Answer the following questions:
a) if the maximum error of estimate is 0.04 for this sample, what would be the sample size?
b) given that the sample size is 400 with this same z(a/2) and 0, what would be the Maixmum Error of estimate?
c) what happens to the maximum error of estimate as the sample size gets smaller?
d) what effect does the answer to C above have to the size of the confidence interval?
Click here to see answer by stanbon(57966) |
Question 612666: Determine the critical region and critical values for z that would be used to test the null hypothesis at the given level of significance, as described in each of the following:
(A)Ho:u >_ 70 and Ho:u < 70 and a = 0.10
(B) Ho:u <_ 75 and Ho:u . 75 , a = 0.05
(C) Ho:u = 36 and Ha : u =/ 36 , a = 0.01
Click here to see answer by stanbon(57966) |
Question 612748: 1.....2,2,6,7
2.....3,4,4,5,8
3.....3,3,3,5,6
4.....0,0,1,2,2
5.....0,1
I need to know the mode,median & range. These are the following choices:
Mode: Median: Range:
A.33 C.2&3 A.3 C.51 A.39 C.51
B.12 D.40 B.33 D.2 B.12 D.2
Plz Help! Its very confusing.
Click here to see answer by Edwin McCravy(8999)  |
Question 612758: A picture must be taken of the golf team:a coach,a manager,& 5 athletes. If the team must be lined up coach first & manager last, how many different ways can the team be ordered??
Help will be appreciated!
Click here to see answer by edjones(7569)  |
Question 612819: Classify the following as discrete or continuous random variables.
(A) The time it takes to run a marathon
(B) The number of fractions between 1 and 2
(C) A pair of dice is rolled, and the sum to appear on the dice is recorded
(D) The length of a broad jump
Click here to see answer by Theo(3504)  |
Question 612825: How many green elements are required to make this a legitimate probability distribution if there are a total of 50 elements in this sample?
x red blue orange brown green
P(x) 0.10 0.10 0.18 0.22
red is above 0.10 and so on. Green has no number.
Click here to see answer by stanbon(57966) |
Question 612853: Consider the following experiment. Three cards are drawn from a standard deck of 52 cards, one after another. Before the second card is drawn , the first card is put back in the deck and the deck is re-shuffled. Before the third card is drawn, the second card is p0ut back in the deck and reshuffled.
Find the probability that all three cards will be in the suit of hearts.
Click here to see answer by stanbon(57966) |
Question 612851: In the State of OH, 40 percent of all e-mails deal in some way with the depressed U.S. economy. If a random sample of 10 e-mails is selected, what is the probability of the following:
Exactly five e-mails deal in some way with the depressed U.S. economy?
Exactly five e-mails do not deal in some way with the depressed U.S. economy?
More than five or less than two e-mails deal in some way with the depressed U.S. economy?
All 10 e-mails deal in some way with the depressed U.S. economy?
Click here to see answer by stanbon(57966) |
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