Tutors Answer Your Questions about Probability-and-statistics (FREE)
Question 251620: mileage test are conducted on a randomly selected sample of 100 newly developed automobile tires. The average tread wear was found to be 50,000 miles with a standard deviation of 3,500 miles. What is the best estimate of the average tread life in miles for the entire population of these tires?
a. 50,000
b. 3,500
c. 50,000/100
d. 3,500/100
Click here to see answer by stanbon(57967)  |
Question 251672: You know that houses in your school district sell for a mean of $350,000 with a standard deviation of $50,000. Assume they follow a normal distribution. You are looking for a new home in your school district, and want to spend between $280,000 and $340,000. What percentage of homes are within your budget?
Click here to see answer by stanbon(57967) |
Question 251657: for a junit change in the first independent variable with other things being held constant, what change can be expected in the dependent variable in the multiple regression equation Y= 5.2 + 6.3X1-7.1X2
a. -7.1
b. +6.3
c. +5.2
d. +4.4
Click here to see answer by stanbon(57967) |
Question 251656: what is our decision regarding the differences between the observed and expected frequencies if the critical value of cji-squared is 9.488 and the computed value is 6.079
a. the difference is probably due to sampling erroe; do not reject the null hypothesis
b. not due to chance; reject the null hypothesis
c. not due to chance ; do not reject the alternative hypothesis
d. too close; reserve judgement
Click here to see answer by stanbon(57967) |
Question 251655: a preliminary study of hourly wages paid to unskilled employees in three metropolitian areas was conducted. seven employees were included from area a, 9 from area b and 12 from area c. the test statistic was computed to be 4.91. What can we conclude at the .05 level?
a. mean hourly wages of unskilled employees all areas are equal
b. mean hourly wages in at least 2 metropolitian areas are different
c. more degrees of freedom are needed
d. none of these are correct
Click here to see answer by stanbon(57967) |
Question 251654: if an ANOVA test is conducted and the null hypothesis is rejected, what does this indicate?
a. too many degrees of freedom
b. no difference between the population means
c. a difference at least one paor of population means
d. none of the above
Click here to see answer by stanbon(57967) |
Question 251653: 20 randomly selected statistics students were given 15 multiple choice questions and 15 open ended questions all on the same material. the professor was interested in determining which type of questions the students scored higher. This experiment is an example of
a. a one sample test of means
b. a two sample test of means
c. a paired t-test
d. a test pf proportions
Click here to see answer by stanbon(57967) |
Question 251652: if two samples, one of size 14 and the sceond of size 13, are used to test the difference between population means, how many dgrees of freedom are used to find the critical value? Assume the population standard deviations are equal
a. 27
b. 26
c. 25
d. 14
e. 13
Click here to see answer by stanbon(57967) |
Question 251651: adinistering the same test to a group of 15 students and a sceond group of 15 students to see which group scpres higher is an example of
a. a one sample test of means
b. a two sample test of means
c. a paired t-test
d. a test of proportions
Click here to see answer by stanbon(57967) |
Question 251650: which of the following conditions must be met to conduct a test for the difference in two sample means?
a. data must be at least of interval scale
b. populations must be normal
c. variance in the two populations must be equal
d. a and b are correct
e. a, b, and c are correct
Click here to see answer by stanbon(57967) |
Question 251649: a hypothesis will test that two population means are equal. a sample of 10 with a standard deviation of 3 is selected from the first population and a smaple of 3 is selected from the first population. the standard deviations are not equal. testing the claim at the .01 level, what is the critical value? Assume unequal standard deviations
a. 2.845
b. 2.787
c. 2.807
d. 2.977
Click here to see answer by stanbon(57967) |
Question 251641: based on the central limit theoreum, the size of the sampling error is
a. directly related to the sampling size for example the larger the sample size the larger the samplinf error
b. directly related to the population mean for example, the larger the mean , the larger the samling error
c. inversely related to the sampling size for example, the larger the sample size the samller the samplinf error.
d. inversely related to the population standard deviation for example, the smaller the standard deviation , the larger the samplinf error.
Click here to see answer by stanbon(57967) |
Question 251868: I dont know how to utilize 95% confidence and how it works in the problem, thank you!
In 1992, the FAA conducted 86,991 pre-employment drug tests on job applicants who were to be engaged in safety and security-related jobs, and found that 1,143 were positive. (a) Construct a 95 percent confidence interval for the population proportion of positive drug tests. (b) Why is the normality assumption not a problem, despite the very small value of p?
Click here to see answer by stanbon(57967) |
Question 251866: I need help with word problems, thank you!
The caffeine content of a cup of home-brewed coffee is a normally distributed random variable with a mean of 115 mg with a standard deviation of 20 mg. (a) What is the probability that a randomly chosen cup of home-brewed coffee will have more than 130 mg of caffeine? (b) Less than 100 mg? (c) A very strong cup of tea has a caffeine content of 91 mg. What is the probability that a cup of coffee will have less caffeine than a very strong cup of tea? (Data are from Popular Science 254, no. 5 [May 1999], p. 95.)
Click here to see answer by stanbon(57967) |
Question 251830: IQs are normally distributed with a mean of 100 and a standard deviation of 15.
If an individual is randomly selected, find the probability that his or her IQ is greater than 120.
Find the IQ that separates the lower 70% of the scores from the upper 30%.
Find the probability that 64 randomly selected people who have an average IQ that is greater than 105.
Click here to see answer by stanbon(57967) |
Question 251867: I dont uunderstand how to utilize 90% confidence and how it works in the problem, thank you!
A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighed on a very accurate scale. The results in grams were
3.087 3.131 3.241 3.241 3.270 3.353 3.400 3.411 3.437 3.477
(a) Construct a 90 percent confidence interval for the true mean weight. (b) What sample size
would be necessary to estimate the true weight with an error of +/- 0.03 grams with 90 percent confidence?
(c) Discuss the factors which might cause variation in the weight of Tootsie Rolls during manufacture.
Click here to see answer by stanbon(57967) |
Question 251865: I need some help with word problems, thank you!
Daily output of Marathon’s Garyville, Lousiana, refinery is normally distributed with a mean of 232,000 barrels of crude oil per day with a standard deviation of 7,000 barrels. (a) What is the probability of producing at least 232,000 barrels? (b) Between 232,000 and 239,000 barrels? (c) Less than 239,000 barrels? (d) Less than 245,000 barrels? (e) More than 225,000 barrels?
Click here to see answer by stanbon(57967) |
Question 251858: You know that houses in your school district sell for a mean of $350,000 with a standard deviation of $50,000. Assume they follow a normal distribution. You are looking for a new home in your school district, and want to spend between $280,000 and $340,000. What percentage of homes are within your budget?
Click here to see answer by stanbon(57967) |
Question 251975: White flies are devastating California crops. An area infested with white flies is to be sprayed with a chemical which is known to be 98% effective for each application. Assume a sample of 1000 flies is checked.
Find the approximate probability that at least 975 of the
flies are killed in one application.
Click here to see answer by stanbon(57967) |
Question 252058: Out of 50 students on student council, 29 are either on the honor roll or write for the school paper. There are 38 student council members who are on the honor roll and 5 that write fo rthe schol paper. What is the probability that a randomly selected student council member is both on the honor roll and writes for the schoo paper?
Click here to see answer by solver91311(17077)  |
Question 251974: The probability that a small business will go bankrupt in its first year is .21. For 50 such small businesses, find the following probabilities first by using the binomial probability formula, and then by using the normal
approximation.
a. Exactly 8 go bankrupt.
b. No more than 2 go bankrupt.
Click here to see answer by stanbon(57967) |
Question 252028: Question 1: a) The sales Manager of an Automobile dealer estimated 80% of the new cars delivered by them have no defect and so will not be brought back immediately for repair. He sells a fleet of 10 cars to an important customer. What i»the probability that — (i) No car will be brought back (ii) Exactly two cars will be brought back. (iii) At least two cars will be brought back.
b) State the laws of probability.
c) Describe giving examples different types of events.
Click here to see answer by stanbon(57967) |
Question 252107: A box contains fewer than 50 marbles. Each marble is either red or white. The probability of randomly choosing a red marble is 2/5. What is the largest number of white marbles that could be in the box?
A 18 b 27 c 31 d 45 e 49
Click here to see answer by vksarvepalli(154)  |
Question 252101: a die is loaded in such a way that the probabilityof the face with j dots turning up is proportional to j for j=1,2,3,4,5,6. in 6 independent throws of this die , what is the probability that each face turns up exactly one?
Click here to see answer by vksarvepalli(154) |
Question 252130: A box contains 2 green and 3 white balls. A ball is selected at random from the box. If the ball is green, a card is drawn from a deck of 52 ca rdto. If the ball is white, a card is drawn from the deck consisting of just the 16 pictures. (a) What is the probability of drawing a. king? (b) What is the probability of a white ball was selected given that a king was drawn?
Click here to see answer by Edwin McCravy(8999)  |
Question 252145: A pair of dice consisting of a six-sided die and a four-sided die is rolled and the sum is determined. Let A be the event that a sum of 5 is rolled and let B be the event that a sum of 5 or a sum of 9 is rolled. Find (a) P(A), (b) P(B), and (c) P(A n B).
Click here to see answer by edjones(7569)  |
Question 252145: A pair of dice consisting of a six-sided die and a four-sided die is rolled and the sum is determined. Let A be the event that a sum of 5 is rolled and let B be the event that a sum of 5 or a sum of 9 is rolled. Find (a) P(A), (b) P(B), and (c) P(A n B).
Click here to see answer by drk(1908) |
Question 252139: A company installs 5000 light bulbs, each with an average life of 500 hours, standard deviation of 100 hours, and distribution approximated by a normal curve. Find the percentage of bulbs that can be expected to last the period between:
a) 290 hours and 500 hours.
b) 540 hours and 780 hours.
Click here to see answer by stanbon(57967) |
Question 252177: A bag contains a total of 14 balls: 4 red balls, 3 blue balls and 7 white balls. Two balls are drawn at random without replacement.What is the probability that both balls are red?
a 6/91 b 9/182 c 6/92 d 12/92 e 9/196
Click here to see answer by richwmiller(9144)  |
Question 252177: A bag contains a total of 14 balls: 4 red balls, 3 blue balls and 7 white balls. Two balls are drawn at random without replacement.What is the probability that both balls are red?
a 6/91 b 9/182 c 6/92 d 12/92 e 9/196
Click here to see answer by checkley77(12569) |
Question 252181: The sales Manager of an Automobile dealer estimated 80% of the new cars delivered by them have no defect and so will not be brought back immediately for repair. He sells a fleet of 10 cars to an important customer. What i»the probability that — (i) No car will be brought back (ii) Exactly two cars will be brought back. (iii) At least two cars will be brought back.
Click here to see answer by edjones(7569) |
Question 251780: Interpret the type of correlation by completing the table below and calculating the correlation coefficient r. Round the correlation coefficient to two decimal places. Interim rounding should be four decimal places. Outcome 3
x y xy x^2 y^2
38 116
41 120
45 123
48 131
51 142
53 145
57 148
61 150
65 152
Click here to see answer by drk(1908) |
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