Tutors Answer Your Questions about Probability-and-statistics (FREE)
Question 464998: How many ways are there to select a committee to develop a discrete mathematics course at a university if the committee is to consist of four faculty members from the mathematics department and three from the computer science department, if there are 10 faculty members of the mathematics department and 12 of the computer science department?
Click here to see answer by edjones(7569)   |
Question 465006: K. Historically, the campus police write a ticket on 15% of the vehicles they stop on campus; violations include speeding, no valid sticker, illegal parking, etc. Student leaders will take a survey of 400 students who had been stopped by the campus police. What is the probability that 55 or more of these students have been issued a ticket? Note: Be sure to identify any assumptions or conditions needed
Click here to see answer by stanbon(57347) |
Question 465006: K. Historically, the campus police write a ticket on 15% of the vehicles they stop on campus; violations include speeding, no valid sticker, illegal parking, etc. Student leaders will take a survey of 400 students who had been stopped by the campus police. What is the probability that 55 or more of these students have been issued a ticket? Note: Be sure to identify any assumptions or conditions needed
Click here to see answer by edjones(7569) |
Question 465000: Why can we not draw causal conclusions based on correlations among variables? In other words, explain why the phrase, “Correlation does not imply causation” is true. Identify an example from real life (i.e., work, politics, family life) where there is an apparent relationship between two behaviors and discuss the possible explanations for that relationship.
Click here to see answer by stanbon(57347) |
Question 464970: A certain brand of cookie is sold in a package containing six cookies. Sometimes the cookies are broken. Present the probability distribution for the number of broken (defective) cookies in a package when the defective rate is 30%. Describe the shape of the histogram. Determine each of the following: mean, median, mode, range, and standard deviation. Find the probability that the number of broken cookies in the package is more than 2.
Click here to see answer by edjones(7569) |
Question 465156: assuming that the mean systolic blood pressure of a normal adult is 120 millimeters of mercury(mmHg)and the standard deviation is 5.6. assume the variable is normally distributed,
i). if an individual is selected, find the probability the individual's pressure will be between 120 and 121.8 mmHg
ii). if a sample of 30 adults is randomly selected, find the probability that the sample mean will be between will be between 120 and 121.8 mmHg
Click here to see answer by edjones(7569) |
Question 465155: in a certain hospital, maternity, it has been observed that the probability of getting a baby boy is 0.32. if 10 expectant ladies are observed, find the probability that,
i) exactly three of them are males
ii)at least 9 are females
iii) none is a boy
Click here to see answer by edjones(7569) |
Question 465161: How many ways are there to select a committee to develop a discrete mathematics course at a university if the committee is to consist of four faculty members from the mathematics department and three from the computer science department, if there are 10 faculty members of the mathematics department and 12 of the computer science department?
Click here to see answer by edjones(7569) |
Question 465167: the frequency distribution of scores on an examination is closely described by a bell shaped frequency curve and the distribution has a mean of 57.5 and a standard deviation of 10.
i) what percentage of candidates would be awarded grade A if the cut-off for grade A is 75 Marks?
Click here to see answer by stanbon(57347) |
Question 465186: Suppose that the reliability of a test for hepitisus is specified as follows. Of the people with hepatitis 96% have a positive reaction and 4% have a negative reacti0on, of the people free of hepititis, 95% have a negative reaction and 5% have a positive reation. From a large population of witch 0.05% of the people have hepititis , A PERSON IS SELECTED AT RANDOM AND IS GIVEN THE TEST IS POSITIVE, WHAT IS THE PROBABILITY THAT THE PERSON ACTUALLY HAS HEPITITIS?
Click here to see answer by stanbon(57347) |
Question 465190: Joe feels the probability of getting an A in history is .3, the probability of getting a A in physcology is 0.4, and the probability of getting an A in history or Physcology is 0.6 . What is the probability of getting an A IN BOTH SUBJECTS?
Click here to see answer by stanbon(57347) |
Question 465198: three horses calle A,B,C are all racing aginst each other the probability that A will win is 1/7 the probability that B will win is 1/3. What is the probability that c will win?? Also what is the odds that C will win 11 to___?
Click here to see answer by stanbon(57347) |
Question 465244: Hello, I do not understand this question at all. I do not really understand Statistics at all honestly. If you could help me I would greatly appreciate it! :) Thank you!
Why can we not draw causal conclusions based on correlations among variables? In other words, explain why the phrase, “Correlation does not imply causation” is true. Identify an example from real life (i.e., work, politics, family life) where there is an apparent relationship between two behaviors and discuss the possible explanations for that relationship.
Click here to see answer by stanbon(57347) |
Question 465267: victoria goes to the deli for sandwiches and orders 5 roast beefs and 4 ham sandwiches. They are wrapped and put into a paper bag. What is the probability that two sandiches choosen at random will be a roast beef ? What is the probability that the two sandwiches will be alike??
Click here to see answer by ewatrrr(10682)  |
Question 464210: A college requires applicants to have an ACT score in the top 12% of all test scores. The ACT scores are normally distributed, with a mean of 21.5 and a standard deviation of 4.7.
i) type of distribution: _sampling distributions of mean______________
ii) find the mean: __21.5 points________ and standard deviation: ____4.7 points______
iii) find the following:
a. Find the lowest test score that a student could get and still meet the college’s requirement.
b. If 1300 students are randomly selected, how many would be expected to have a test score that would meet the college’s requirement?
c. How does the answer to part (a) change if the college decided to accept the top 15% of all test scores?
Click here to see answer by stanbon(57347) |
Question 464211: The weight of potato chips in a medium size bag is stated to be 8 ounces. The amount that the packaging machine puts in these bags is believed to be normally distributed with a mean of 8.2 ounces and standard deviation of 0.12 ounces.
i) type of distribution: __sample distributions of sample_____________
ii) find the mean of the population: _8.2 ounces______ and standard deviation of the population: ___.12 ounces______
iii) find the probability of a bag sold that is underweight. 4.78%__________
iv) Some of the chips are sold in “bargain packs” of 3 bags. Find the mean of the distribution of mean of all bargain packs: 8.2 ounces_______ and standard deviation: _.0693 ounces________
v) What’s the probability that the mean of the 3 is underweight? ___normalcdf(-1E99, 8, 8.2, .0693)= .001951?________
vi) What’s the probability that the mean weight of 24-bag case of potato chips is below 8 ounces? __________
Click here to see answer by stanbon(57347) |
Question 465346: An urn contains 8 balls identical in every way except color. There are 4 blue balls, 3 red balls, and 1 yellow ball.
a) You draw 2 balls from the urn but replace the first before drawing the second. What is the probability that both balls are red?
b) You draw 2 balls from the urn but do not replace the first before drawing the second. What is the probability that both balls are red?
c) Explain the difference (if any) in the two problems.
Click here to see answer by ewatrrr(10682) |
Question 465315: 1. Suppose you decide to bet on red on each of 10 consecutive spins of the roulette wheel. Suppose you lose all five of the first wagers, which means that on the first five spins of the wheel, red has not come up once. Which of the following is true?
A. The wheel is not working properly. It favors outcomes that are not red. Hence, during the next five spins of the wheel, we’re likely to continue to see few red outcomes.
B. What happened on the first five spins tells us nothing about what will happen on the next five spins.
C. We’re due for a win, so the sixth spin of the wheel is very likely to come up red.
D. You should get more spins of red on the next five spins of the wheel because we didn’t get any on the first five spins.
Click here to see answer by stanbon(57347) |
Question 465433: A psychologist wants to interview subjects with IQ scores in the top 1%. IQ scores are normally distributed with mean of 100 and a standard deviation of 15. Find the score that separating the top 1% of IQ from the bottom 99%.
Click here to see answer by stanbon(57347) |
Question 465432: The Ivy College Technology Center reports that 80% of the incoming freshmen purchase a printer from the Center, 35% buy a laptop from the Center, and that 60% of those who buy a laptop from the Center also buy a printer there. What is the probability that a randomly selected freshman student
a) purchased a laptop computer and a printer from the Center?
b) purchased a laptop computer or a printer from the Center?
c) purchased a laptop at the Center, given that (s)he purchased a printer there?
Click here to see answer by jorel1380(2518)  |
Question 465430: Suppose A and B are events with P(A) = 1/4, P(B) = 2/5, and P(A or B) = 1/2.
a) Are the events A and B mutually exclusive? Explain your reasoning.
b) What is P(A and B)?
c) Are the events A and B independent? Explain your reasoning.
Click here to see answer by robertb(4012)  |
Question 465430: Suppose A and B are events with P(A) = 1/4, P(B) = 2/5, and P(A or B) = 1/2.
a) Are the events A and B mutually exclusive? Explain your reasoning.
b) What is P(A and B)?
c) Are the events A and B independent? Explain your reasoning.
Click here to see answer by stanbon(57347) |
Question 465331: Suppose A and B are events with P(A) = 1/4, P(B) = 2/5, and P(A or B) = 1/2.
a) Are the events A and B mutually exclusive? Explain your reasoning.
b) What is P(A and B)?
c) Are the events A and B independent? Explain your reasoning.
Click here to see answer by stanbon(57347) |
Question 465499: I'm stuck on this :/ some one please help
SAT verbal scores are normally distributed with a mean of 430 and a standard deviation of 120 If 1 of the student is randomly selected, find the probability that he or she obtained a score higher than 440.
Click here to see answer by edjones(7569) |
Question 465475: SAT verbal scores are normally distributed with a mean of 430 and a standard deviation of 120
If 1 of the student is randomly selected, find the probability that he or she obtained a score higher than 440.
Click here to see answer by edjones(7569) |
Question 465510: A study found that the average life expectancy is 53 years with a standard deviation of 7.5 years. If a person is selected at random, what is the probability that the person will die before the age of 65?
A. 94.52%
B. 82.89%
C. 94.95%
D. 88.49%
Click here to see answer by edjones(7569) |
Question 465440: According to the Sleep Foundation, the average night's sleep is 6.8 hours (Fortune, March 20, 2006). Assume the standard deviation is .7 hours and that the probability distribution is normal.
What is the probability that a randomly selected person sleeps more than 8 hours (to 4 decimals)?
What is the probability that a randomly selected person sleeps 6 hours or less (to 4 decimals)?
Doctors suggest getting between 7 and 9 hours of sleep each night. What percentage of the population gets this much sleep (to the nearest whole number)?
%
Click here to see answer by edjones(7569) |
Question 465550: the nursing club at a large college in nairobi believes that the group consists of 10% first years, 20% second years, 40% third years and 30% fourth years. the membership for the club this year consisted of 14 first years, 19 second years, 51 third years and 16 fourth years. at ᾰ=10% test the advisers conjecture
Click here to see answer by stanbon(57347) |
Question 465602: 25.If the variance of a random variable X is given Var(X)=3. Then Var(2X) is
30.The lifetime of a machine part has a continuous distribution on the interval (0, 40) with probability density function . Calculate the probability that the lifetime of the machine part is less than 6.
31.The lifetime of a machine part has a continuous distribution on the interval (0, 40) with probability density function . Calculate the probability that the lifetime of the machine part is less than 5.
32.If Var(X)=2, find Var(-3X+4).
Click here to see answer by stanbon(57347) |
Question 465601: Problem 9.52
At Ajax Spring Water, a half-liter bottle of soft drink is supposed to contain a mean of 520 ml. The filling process follows a normal distribution with a known process standard deviation of 4 ml.
A) Which sampling distribution would you use if random supplies of 10 bottles are to be weighed?
B) Set up hypotheses and a two-tailed decision rule for the correct mean using the 5% level of significance.
C) If sample of 16 bottles shows a mean fill of 515ml, does this contradict the hypothesis that the true mean is 520ml?
Click here to see answer by stanbon(57347) |
Question 465606: Tomorrow I have exam and I must solve this problem. Please, help me.
37. Marks on a Chemistry test follow a normal distribution with a mean of 65 and a standard deviation of 12. Approximately what percentage of the students have scores below 50?
38. Suppose the test scores of 600 students are normally distributed with a mean of 76 and standard deviation of 8. The number of students scoring between 70 and 82 is:
39. The distribution of weights in a large group is approximately normally distributed. The mean is 80 kg. and approximately 68% of the weights are between 70 and 90 kg. The standard deviation of the distribution of weights is equal to:
43. A continuous random variable X is uniformly distributed over the interval [10, 16]. The expected value of X is
45. How many different three-member teams can be formed from six students?
46. How many different 6-letter arrangements can be formed using the letters in the word ABSENT, if each letter is used only once?
47. If P(E) is the probability that an event will occur, which of the followings must be false?
48. A die is rolled. What is the probability that the number rolled is greater than 2 and even?
49. A pair of dice is rolled. A possible event is rolling a multiple of 5. What is the probability of the complement of this event?
55. A pair of dice is rolled. A possible event is rolling a multiple of 5. What is the probability of the complement of this event?
56. Your state issues license plates consisting of letters and numbers. There are 26 letters and the letters may be repeated. There are 10 digits and the digits may be repeated. How many possible license plates can be issued with two letters followed by three numbers?
58. A fair coin is thrown in the air four times. If the coin lands with the head up on the first three tosses, what is the probability that the coin will land with the head up on the fourth toss?
59. A movie theater sells 3 sizes of popcorn (small, medium, and large) with 3 choices of toppings (no butter, butter, extra butter). How many possible ways can a bag of popcorn be purchased?
63. Heights of college women have a distribution that can be approximated by a normal curve with a mean of 65 inches and a standard deviation equal to 3 inches. About what proportion of college women are between 65 and 67 inches tall?
64. The probability is p = 0.80 that a patient with a certain disease will be successfully treated with a new medical treatment. Suppose that the treatment is used on 40 patients. What is the "expected value" of the number of patients who are successfully treated?
65. A medical treatment has a success rate of 0.8. Two patients will be treated with this treatment. Assuming the results are independent for the two patients, what is the probability that neither one of them will be successfully cured?
66. A set of possible values that a random variable can assume and their associated probabilities of occurrence are referred to as ...
70. Two events each have probability 0.2 of occurring and are independent. The probability that neither occur is
71. A smoke-detector system consists of two parts A and B. If smoke occurs then the item A detects it with probability 0.95, the item B detects it with probability 0.98 whereas both of them detect it with probability 0.94. What is the probability that the smoke will not be detected?
73. A company which produces a particular drug has two factories, A and B. 30% of the drug are made in factory A, 70% in factory B. Suppose that 95% of the drugs produced by the factory A meet specifications while only 75% of the drugs produced by the factory B meet specifications. If I buy the drug, what is the probability that it meets specifications?
74. Twelve items are independently sampled from a production line. If the probability any given item is defective is 0.1, the probability of at most two defectives in the sample is closest to …
75. A student can solve 6 from a list of 10 problems. For an exam 8 questions are selected at random from the list. What is the probability that the student will solve exactly five problems?
76. Suppose that 10% of people are left handed. If 8 people are selected at random, what is the probability that exactly 2 of them are left handed?
77. Suppose a computer chip manufacturer rejects 15% of the chips produced because they fail presale testing. If you test 4 chips, what is the probability that not all of the chips fail?
Click here to see answer by stanbon(57347) |
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