Tutors Answer Your Questions about Probability-and-statistics (FREE)
Question 1995: Thank you for being there! I'm numerically-challenged and plagued by instincts I can't make work for me. I am trying to calculate an overall aggregate recidivism rate for three distinct groups of kids. Each group has a distinct recidivism rate, but I need to meld them into an overall average weighted rate. Here are my numbers for your pleasure (pleasure?):
17 kids with a 12 percent recidivism rate
19 kids with a 37 percent recidivism rate
22 kids with a 55 percent recidivism rate
Question? What is the average recidivism rate for all these 58 kids?
I'll treat you to lunch if you can back to me quickly; I'm preparing a summary report for our judges and there ain't a mathematician in the courthouse! WP, administrator of Re-Entry Court.
wally9542@cox.net
Click here to see answer by longjonsilver(2297)   |
Question 2360: Can some help me on this question of probability? Please show your work.
For this question pretend you are drawing cards without replacement from the infamous "Iraq's Most Wanted" deck issued by the U.S. Military. If you are drawing from the full deck of 55 cards, what are the following probabilities:
a. You draw a card that is not Saddam Hussein
b. You draw three cards, which end up being Saddam Hussein and his two sons.
c. You draw 14 cards and not one of them is Saddam Hussein.
Click here to see answer by longjonsilver(2297) |
Question 2359: I have two probability questions that really through me a loop. Can someone answer the questions and show there work? I appreciate any help.
Thanks
1. Suppose you have 3 nickels, 2 dimes, and 6 quarters in your pocket. If you draw a coin randomly from your pocket, what is the probability that
a. You will draw a dime?
b. You will draw a half-dollar?
c. You will draw a quarter?
2. You are rolling a pair of dice, one red and one green. What is the probability of the following outcomes:
a. The sum of the two numbers you roll from the dice is 11.
b. The sum of the two numbers you roll is 7.
c. The sum of the two numbers you roll is 13.
Click here to see answer by longjonsilver(2297) |
Question 4013: One point is scored for each successful shot. So the player can end up with 0 points(by missing the first shot), q point (by making first shot but not second shot), or 2 points (by making both shots).
Terry is a basketball player who has shown over a period of time that she makes about 60% of the free throws she attemps.
Now suppose that Terry is in a one-on-one situation. How many points is she most likely to score: 1, 2, 3?
Click here to see answer by longjonsilver(2297) |
Question 4613: Hi. The problem is: "Find the probability that two parents with three children have all girls." I have already found out that the answer is 1/8, and how to set the problem up to get that answer, but I just don't understand WHY!! To me, it makes more sense to have it be 1/2 - you have three kids, and each one could be male or female. So, you have three chances/six outcomes. I just don't get why having a boy boy girl, a boy girl boy, or a girl boy boy should be considered as different. Either way, you are having two boys, one girl. Likewise the boy girl girl, girl boy girl, and girl girl boy. You still have the same outcome - one boy, two girls. HELP! If I can't get the logic, I won't be able to sleep : }. Thank you! Maggie
Click here to see answer by longjonsilver(2297) |
Question 4857: An insect trap catches an average of four insects per 20 minute. Assuming that insects are caught randomly and independently, what is the probability that in a randomly chosen 20 minute period:
A) exactly five insects will be caught?
B) no more than two insects will be caught?
c) at least four insects will be caught?
D) over a randomly chosen one hour period what is the probability that exactly 10 insects will be caught?
The body temperature of a population of mammals are known to be normally distributed with a mean of 37.2 degrees and a standard deviation of 0.35 degress.
A) what proportion of the population have a tempreture of
i) more than 39 degrees ?
ii) less than 36.8 degrees?
iii) between 36.5 degrees and 38.5 degrees?
I will be very grateful if you could help me with these questions please.
Thank you very much
Birgul....
Click here to see answer by khwang(438) |
Question 5081: Help--how do i figure this one out? Driving me crazy !!!
Twenty bearded men gather. Ten have eight-inch beards, six have ten-inch beards, and four have twelve-inch beards. What is the expected length of a randomly selected man from this group?
Tried 10/20 x 6/20 x 4/20 =12inches, that doesn't seem right. Please help!
Click here to see answer by rapaljer(4667)  |
Question 5081: Help--how do i figure this one out? Driving me crazy !!!
Twenty bearded men gather. Ten have eight-inch beards, six have ten-inch beards, and four have twelve-inch beards. What is the expected length of a randomly selected man from this group?
Tried 10/20 x 6/20 x 4/20 =12inches, that doesn't seem right. Please help!
Click here to see answer by apeokukuy2k(1) |
Question 5927: If I roll 5 regular dice out of a cup, what is
1. The probability that I will get 5 of a kind. I think the answer is 1 in 1296.
2. What is the probability that I will get two pair, i.e., 22335, 55422, even 33433 would count as two pair. I come up with 1 in 34.56 rolls but I don't think this is correct.
Thanks,
Bob Boose
Click here to see answer by khwang(438) |
Question 9120: A jar of contains 3 red, 5 white, and 2 blue marbles.A marble is drawn.What is the probability that the marble is blue? the answer is....1/4, 1/45, 1/3, or none of these? thank you for the help!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Click here to see answer by longjonsilver(2297) |
Question 9444: Question: In a multiple-choice test wtih 5 questions, each question has 3 possible answers. What is the total number of ways the questions could be answered?
I'm using a TI-83. I entered 5nCr3 and was given 10 as the answer, but this is too low. What am I doing wrong?
Click here to see answer by rapaljer(4667) |
Question 11183: he probability that a bank customer will default on a loan is 0.04 if the economy is good and 0.13 if the economy is not good. Suppose the probability that the economy will be good is 0.65. What is the probability that the person will default on the loan?
Click here to see answer by longjonsilver(2297) |
Question 11398: Dear tutor, for whatever reason i cannot figure out this probability question. Can you help? Here it goes:
Jack Jockely got up late one morning and was trying to find a clean pair of socks. He has a total of six pairs (three maroon and three white) in his drawer. Jack is not a very good housekeeper and his socks were just thrown in the drawer and, to make the morning perfect, the lightbulb is burned out so he can't see. How many socks does he have to pull out of the drawer before he gets a matched pair (two maroon socks or two white socks)?
Click here to see answer by askmemath(368) |
Question 11504: Assume that male and female borths are eqaully likely and that the birth of any child does not affect the probability of the gender of any other children. Find the probability of exactly seven boys in ten births.
Click here to see answer by khwang(438) |
Question 11681: The lengths of pregnancies of humans are normally distributed with a mean of 268 days and a standard deviation of 15 days. A baby is premature if it is born three weeks early. What percentage of babies are born prematurely?
Click here to see answer by khwang(438) |
Question 12369: a teacher has a set of 12 problems to use on a math exam. The teacher makes different versions of the exam by putting 10 questions on each exam. How many different exams can the teacher make?
Click here to see answer by kusha(21) |
Question 13320: A circular spinner has a blue sector with a centra angle of 72 degrees, a green sector with 144 degree angle, a yellow sector with a 36 degree angle and a red sector with a 108 degree angle. For the described event, give the probablility as a percent.
The spinner is spun twice. It lands on red, then green. ____12%____
The spinner is spun twice. It lands on red once, and green once. _____12%____
Let A be the event that the spinner lands on green (one spin), and B be the event that it done not land on green.
a. Find P(A)_____ b. Find P(B)______ c. Find P(a not union B). ________
d. Are A and B independent events? ______________
Click here to see answer by longjonsilver(2297) |
Question 14321: years: 1930, 1940, 1950; 1960; 1970, 1980, 1990
workers:29.4, 32.3, 45.2, 54.2, 70.9, 90.6, 103.9
(millions)
Let x equal the number of years since 1990. Find the line of regression. How many pairs of points can be formed from the 7 data points in the table?
Can you please help me solve this?
Click here to see answer by khwang(438) |
Question 14603: I have two probability questions that really through me a loop. Can someone answer the questions and show there work? I appreciate any help.
Thanks
a) The ventilation system at a power station only functions properly if both machines A and B are working. The probabilities of failure for these machines are 0.07 and 0.03 based on simulation studies. If the machines operate independently, what is the probability that the ventilation system breaks down?
b) An alternative system is based on machones C and D, which both have probability of 0.22 of failing and again operate independently. The ventilation system will function properly so long as either (or both) of machines C AND D is working, what is the probability that the system fails?
Click here to see answer by longjonsilver(2297) |
Question 14601: A class of twenty students consists of eight males and twelve females. Two students are selected at random. By considering the events A=' the first student is male' and B= 'the second student is male' evaluate the possibilities of these events:
a) C= 'both students are male'
b) D= 'both students are female'
c) E= 'one male and one female chosen'
Please could you help me with the question above, I know that the probability of selecting a male first is 8/20 and selecting second is 7/19, but would appreciate it if someone could help me how to work out the other events.
Thanks
Sam
Click here to see answer by longjonsilver(2297) |
Question 14780: Hi I really need help answering couple of questions, please could someone explain them to me?
1) In a batch of a hundred light bulbs there are 5 bad bulbs. Inspectors inspects 10 at random. Compute probability of finding at least one defective light bulb.
2)Eighty percent of a population with coronary disease have chest pain symptoms and twenty five percent without the disease have chest pain symptoms. A person visits the doctor with the chest pain symptom, what are the probabilities of the following events?
a)person has coronary disease
b)person does not have coronary disease.
Click here to see answer by khwang(438) |
Question 15532: I submitted this problem Friday evening and I got no response. I need to know if I'm right or wrong, it's due tomorrow.
If 10 cards are drawn without replacement from an ordinary deck, find the probability of obtaining exactly 3 aces or exactly 3 kings (or both). I tried
using (52 choose 10) for the denominator and (10 choose 3)^4 for the numerator(4 for each suite). It seems as though I'm missing something. Please help asap.
Click here to see answer by venugopalramana(3286) |
Question 15704: Hi,
I'm trying to solve this problem: If a 3-digit number (000 to 999) is chosen at random, find the probability that exactly one digit will be less than 2.
I got to the point of (1/10)^2 * 2/10 but I'm not sure or am I answering another problem. Please help asap.
Click here to see answer by venugopalramana(3286) |
Question 15856: One couple attracted media attention when their 3 children, born in differnet years were born on July 4, ignoring the leap years, find the probability that 3 randomly selected people were all born on July 4?
Click here to see answer by rapaljer(4667) |
Question 18442: Thank you for this great opportunity. My excersice is as follows:
Applications of the Standard Normal Distribution
You are given that a score of 87 on an exam is at 94th percentile and that grades are normally distributed.
a) What z score does this represent? I got .94 = 1.555
b) "This is where i have a problem, Given the formula x = SD*Z + mean," If the mean score on the exam is 82, what is the standard deviation?.
Thank you very much for your help (Due date Saturday November 5th/2005)
Regards
Edwin
Click here to see answer by khwang(438) |
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