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Tutors Answer Your Questions about Probability-and-statistics (FREE)
Question 77019: Statistics. Sam must have an average of 70 or more in his summer course to
obtain a grade of C. His first three test grades were 75, 63, and 68. how do I an inequality representing the score that Sam must get on the last test to get a C grade.
Click here to see answer by stanbon(26259)   |
Question 76817: in a bag are 7 pennies, 4 nickels, and 5 dimes. three coins are selected at random. find the probability of each of the following selections.
a.all 3 pennies b.all 3 nickels c.all 3 dimes d.2 pennies,1 dime e.1 penny,1 dime,1 nickel f.1 dime, 2 nickels
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Question 76798: I am trying to help my child and I am stuck on this question. Please help
A plastics company has extended its warranty policy. The policy says that the product will perform a min of 5,000 hrs. If they have a failure before that time, a refund of 25.00 will be given. The failure distribution for this line is X=6250 hours and sigma= 700 hours.1)If the company sells 10,000 units what cost could be expected from the policy? 2) What alternatives are available to control the failures at 1/2 of 1%?
I appreciate it.
Click here to see answer by stanbon(26259) |
Question 76412: Compute the missing frequencies in the frequency distribution table given below which is partly produced based on 100 observations for which the mean was found to 1.86.
Accidents 0 1 2 3 4 5
Frequency 36 ? ? 15 5 5
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Question 77462This question is from textbook 
: hi i have this homework with a statistics problem or anyone to ask how to formulate it. can you help me? i am so stuck. thanks
T=3(A-20)^2 divided by 50+10
formula describes the average running time, T,l in seconds, for a person who is A years old to run the 100-yard dash. How long soes it tak,e a 30-year old runner to run the 110-yard dash?
this is our first week of class and we havent been taught how to do this problem?????????This question is from textbook
Click here to see answer by stanbon(26259) |
Question 77800: I am having a very hard time with this problem! Please help!
The time a group of high school students arrive home from school each day was found to be normally distributed. The mean time was 3:15 PM and the times had a standard deviation of 15 minutes. What is the probability that a student chosed at random arrives home from school before 2:30 PM?
Click here to see answer by stanbon(26259) |
Question 77826: Grace has 16 jellybeans in her pocket. She has 8 red ones, 4 green ones, and 4 blue ones. What is the minimum number of jellybeans she must take out of her pocket to ensure that she has one of each color? Thanks so much for your help!
Click here to see answer by ashquackenbush(1) |
Question 78322: A drawer contains 4 red socks, 6 white socks, and 10 blue socks. Without looking, you draw out a sock and then draw out a second sock without returning the first sock. What is the probability that the first sock and the second sock are both white.
Click here to see answer by stanbon(26259) |
Question 78387: A class is given a list of 20 study problems from which 10 will be chosen as part of an upcoming exam.A given student knows how to solve 15 of the problems.Find the probability that the student will be able to answer
a. all 10 questions on the exam
b. exactly 8 questions on the exam
c. at least 9 questions on the exam
Click here to see answer by stanbon(26259) |
Question 78437: In the "firrst quater of the year" means Januryary,Febrruary, and March. The "second quater" is April,May,and June.
Achme Reaaltors sold 23 houses during the first quater of the year and again duyring the last quater. Sales during the middle quater was not quite as good, so that tht the annual sales was 57 houses. b &B realty compaly sold 50 homes during the second quater and hald that many during the forth quater, for a total annual sales of 75 homes. Arco sold as many houes during the thurd quater as B&B sold during the entire year, but during the other three quaters they did no better then b&b during the first quater. Toget the tgree cinoabues sikd 79 giyses during the third quater.
How many houses did the three companies sell during the second quater?
Click here to see answer by stanbon(26259) |
Question 78436: In the "firrst quater of the year" means Januryary,Febrruary, and March. The "second quater" is April,May,and June.
Achme Reaaltors sold 23 houses during the first quater of the year and again duyring the last quater. Sales during the middle quater was not quite as good, so that tht the annual sales was 57 houses. b &B realty compaly sold 50 homes during the second quater and hald that many during the forth quater, for a total annual sales of 75 homes. Arco sold as many houes during the thurd quater as B&B sold during the entire year, but during the other three quaters they did no better then b&b during the first quater. Toget the tgree cinoabues sikd 79 giyses during the third quater.
How many houses did the three companies sell during the second quater?
Click here to see answer by stanbon(26259) |
Question 78624: You have a very important job interview at 8:00 AM tomorrow. Unfortunately, you do not have a reliable alarm clock. In fact,the three alarm clocks you have only ring some of the time. The first clock only rings 20% of the time, the second clock only rings 30% of the time, and the third clock only rings 50% of the time. If you set each of them to ring at 6:30 AM, what is the probability that you will be alerted to get up at the correct time?
a 0%
b 3%
c 100%
d cannot determine from the given information
e none of the above
Click here to see answer by Edwin McCravy(2920) |
Question 78623: On your way to a particular location that you regularly travel, There are three intersections with traffic lights. Each of the three lights has a different stop and go pattern: Light one is green 10% of the time, light two is green 40% of the time, and light three is green 25% of the time. Assuming that you are a very safe driver and only drive through an intersection when the light is green, what is the probability that you will arrive at your destination without having to stop(that is,hitting all three traffic lights green)?
a 1%
b 25%
c 75%
d 100%
e none of the above
Click here to see answer by bucky(1732) |
Question 79070: The formula G=~(2.5+357) and L=7.43~(x-115) model the loan amounts, in billions of dollars, to college students for grants, G, and loans, L, x years after 1970. In which year was the amount from loans the same as the amount from grants? Please show your work.
Click here to see answer by stanbon(26259) |
Question 79024: The numbers 1 to 10 are written on sheets of paper and placed in a hat. If one sheet of paper is selected at random then find the following:
The probability the nember is greater than 3
A. 1/10
B. 3/10
C. 8/10
D. 7/10
The odds the number is a 9
A. 1:9
B. 1:10
C. 1:11
D. 1:1
The probability the number is odd OR greater than 3.
A. 9/10
B. 7/20
C. 12/10
D. 3/10
The probability the number is odd AND less than 5
A. 9/10
B. 7/10
C. 1/5
D. 4/5
Click here to see answer by stanbon(26259) |
Question 79023: Of the 30 people to order drinks in a restaurant, 7 of them ordered tea, 10 ordered coke, and 13 ordered water.
What is the empirical probability the next order will be a coke?
A. 1/3
B. 2/3
C. 1:3
D. 7/30
What are the odds that the next person will order water?
A. 13:30
B. 13:17
C. 17:13
D. 17:30
What is the empirical probability the next order is NOT water?
A. 13/30
B. 7/30
C. 17/30
D. 10/30
What is the probability the next two orders are both tea?
A. 14/900
B. 371/900
C. 7/15
D. 49/900
What is the probability the next two orders are coke OR water?
A. 13/90
B. 23/30
C. 7/30
D. 28/45
Click here to see answer by stanbon(26259) |
Question 79019: One card is selected from a deck of standard poker cards (assume a typical deck of 52 total cards numbered from 2 thru 10 and Jack thru Ace) at random. Find the probability the card is a spade OR less than 8 (that is, from 2 to 7 only).
A. 31/52
B. 37/52
C. 39/338
D. 3/26
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Question 79018: The State Pick-3 lottery uses 27 balls numbered 1 to 9 (3 each). What is the probability that my ticket numbered "222" will win? Assme that the balls are not replaced after each selection.
A. 1/19683
B. 1/2925
C. 2/ 6561
D. 1/1
Click here to see answer by stanbon(26259) |
Question 79123: The numbers 1 to 10 are written on sheets of paper and placed in a hat. If two sheets are selected at random then find the following:
The probabilit both numbers are ODD with replacement.
Note: "with replacement" assumes the first selection is replaced back into the hat before the second selection is made.
A. 1/100
B. 1/4
C. 2/9
D. 1/5
The probability both numbers are ODD without replacement.
Note: "without replacement" assumes the first selection is NOT replaced back into the hat, but is held out, while the second selection is made.
A. 1/5
B. 2/9
C. 1/4
D. 1/100
The probability the first number is ODD and the second number is EVEN without replacement.
A. 1/4
B. 5/18
C. 2/9
D. 13/18
The probability of selecting a 2 and then a 9, with replacement.
A 1/4
B. 5/18
C. 2/9
D. 13/18
Click here to see answer by stanbon(26259) |
Question 79126: You select two marbles from a cup with 3 black marbles and 2 marbles. Make an area model to analyze the probabilities.
a. What is the probability of selecting 2 black marbles?
b. What is the probability of selecting 2 blue marbles?
c. What is the probability of selecting a black marble and a blue marble?
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Question 79132: The spinner is spun once. The large sections each have the same area while the small sections are each half the section. What is the probability of scoring:
a. One points
b. two points
c. three points
d. four points
e. five points
f. ten points
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Question 79182: Sale of eggs that are contaminated with salmonella can cause food poisoning among consumers. A large egg producer takes an SRS of 200 eggs from all the eggs shipped in one day. The laboratory reports that 11 of these eggs had salmonella contamination. Unknown to the producer, 0.2% (two-tenths of one percent) of all eggs shipped had salmonella. In this situation
0.2% is a parameter and 11 is a statistic.
11 is a parameter and 0.2% is a statistic.
both 0.2% and 11 are statistics.
both 0.2 % and 11 are parameters.
Click here to see answer by stanbon(26259) |
Question 79346: Mr. Thibodeaux is teaching probability to his class of 48 students. He has 12 decks of cards and 18 pairs of six-sided dice. He wants to divide his class into equal-sized groups. He plans to give each group the same number of decks of cards and the same number of pairs of dice. He also wants to use all of his manipulatives and to have no more than 20 students in each group. How many equal-sized groups are possible? Explain results please.
Click here to see answer by stanbon(26259) |
Question 79369: According to the CDC, if one member of the household contracts the
chickenpox, 90% of family member who have never had the disease or a
vaccine will contract the chickenpox. Suppose four members are exposed
for the first time. What is the probability that three or fewer family
members contract the chickenpox?
Click here to see answer by stanbon(26259) |
Question 79663: Please show me step by step answers on how to solve the 4 problems. Thankyou. It will be greatly appreciated.
Question 1
A researcher wants to estimate the proportion of students at York College who will choose Computer Science as their major in Spring 2008. She wants to be within 5.3% of the actual popultaion proportion and have a 95% level of significance. In a preliminary survey of 42 students 29 said they wanted to take Computer Science in 2008. What is the minimum sample size that she will require? Round final answer up to the next whole number.
Question 2
A fast food restaurant claims that the mean waiting time is not equal to 3 minutes. A random sample of 45 customers revealed a mean waiting time of 3.3 minutes with a standard deviation of 0.7 minutes. Test the restaurants claim at a, a=0.05 level of significance. Assume that the population is normally distributed, and the population standard deviation is 0.7. Use the P-value method.
Question 3: Hypothesis Testing for Proportions.
A researcher at York claims that for Mathematics courses the proportion of grades B or higher was more than 33.0%. In a random sample of 100 grades issued in the year 2006 there were 27 F's, 15 D's, 22 C's, 14 B's, 22 A's. At a=0.10 test the researcher's claim.
Use "rejestion region" claim.
Question 4: Determining sample size
A. A large public university wants to estimate the average(mean) teaching experience of it's faculty. A preliminary random sample of 20 faculty yields a standard deviation of s=2.5 years.
The dean wants to be 95% confident that the sample mean does not have a maximum error of estimate of more than 1.6 years. (Hint: this is maximum error of estimate E). How large of a sample should she use? Use the preliminary sample sample standard deviation as an approximation of the population standard deviation. ROund up to the next whole number.
B. If she decides on a maximum error of estimate of 1.8years. and a level of significance of 95% how large of a sample should she use? Round up to next whole number.
Click here to see answer by stanbon(26259) |
Question 79661: Can someone solve these problems step by step for me. I got them wrong on my last test. ThanYou It will be greatly appreciated.
Question 1 : Confidence Intervals for the Mean
A random sample of 17 students were tested on the SAT english exam. If the mean score was 653.4 with a standard deviation of 135.457, find the 90% confidence interval for the popultation mean. Assume that the population standard deviation in unknown. Assume the scores are approximately normally distributed. Choose the appropriate distribution and state the reason(s) for your choice.Round off your answer to 1 decimal place.
Question 2 : Confidence Interval for a Population Proportion
In a random sample of 50 students enrolled in remedial math courses 21 passed the MAT test by the end of the semester.
A. Calculate the confidence interval for the population percentage of all students in remedial math courses who passed the MAT exam by the end of the semester. Use a 90% level of significance. Round off your final answer to 1 decimal place in percent.
B. If the margin of error is changed to 13.50% and the confidence level remains the same as in Part a, what is the minimum sample size required to estimate the population proportion of students who passed the MAT test? Use the proportions from Part a. Round up the sample size.
Question 3: Hypothesis Testing for the Mean
A sociologist wants to determine if the number of individuals per family unit the national average of 2.9. She interviews 31 randomly selected families in a large apartment complex and obtains a mean of 3.1 individuals per family unit with a standard deviation of 0.80. Test the claim that the mean number of individuals per family unit is less than 2.9. Use a significance level of 0.05. Assume that the population has a normal distribution and that the population standard deviation is unknown. You must decide whether to use the z-test or t-test. If you use the z-test use the P-value method.
Question 4: Confidence intervals for Variance and Standard Deviation
Suppose you are given a sample set of data consisting of 17 body temperatures, with s=1.02. Assume that body temperatures are normally distributed . Find the 95% confidence interval for the population variance 0^2. Round off to 2 decimal places.
Click here to see answer by stanbon(26259) |
Question 79977: Preface: You are going to draw a random marble from a bag containing 5 red marbles, 8 green marbles and two blue marbles.
Question: What is the probability that you draw a red marble?
What are the odds that you draw a blue marble?
Click here to see answer by Edwin McCravy(2920) |
Question 80042: during a difficult release move, a gymnast has fallen from the parallel bars 2 of the 12 competitions this season. the state meet is next week. what is the probability that she will successfully complete the release move?
Click here to see answer by stanbon(26259) |
Question 80068: Question 1
A. A large public university want to estimate the average (mean) teaching experience of it's faculty. A preliminary random sample of 20 faculty yields a standard deviation of s=2.5 years. The dean wants to be 95% confident that the sample does not have a maximum error of estimate of more than 1.6 years. (Hint: this is maximum error of estimate E). How large of a sample should she use? Use the preliminary sample standard deviation as an approximation of the population standard deviation. Round up to next whole number.
B. If she decides on a maximum error of 1.8 years and a level of significance of 95% how large of a sample should she use? Round up to next whole number.
Question 2
Suppose you are given a sample set of data consisting of 17 body temperatures, with s= 1.02. Assume that body temperatures are normally distributed. Find the 95% confidence interval for the population variance. Round off 2 decimal places.
Click here to see answer by stanbon(26259) |
Question 80063: during a game, the pittsburgh steelers converted 4 of 12 fourth downs into first downs. with only minutes left in the game, it is fourth down again and they must make a first down to continue their drive. what is the probability that they will make the first down?
Click here to see answer by stanbon(26259) |
Question 80062: Question 1
A fast food restaurant claims that the mean time is not equal to 3 minutes. A random sample of 45 customers revealed a mean waiting time of 3.3 minutes with a standard deviation of 0.7 minutes. Test the restaurants claim at a, a= 0.05 level of significance. Assume that the population is normally distributed, and the population standard deviation is 0.7. Use the P-value method.
Question 2
A researcher at NYU claims that for Mathematics courses the proportion of grades B or higher was more than 33.0%. In a random sample of 100 grades issued in the year 2006 there were 27 F's, 15 D's, 22 C's, 14 B's, 22 A's. At a=0.10 test the researcher's claim.
Question 3
A sociologist wants to determine if the number of individuals per family unit the national average of 2.9. She interviews 31 randomly selected families in a large apartment complex and obtains a mean of 3.1 individuals per family unit with a standard deviation of 0.80. Test the claim that the mean number of individuals per family unit is less than 2.9. Use a significance level of 0.05. Assume that the population has a normal distribution and that the population standard deviation is unknown. Decide to use the t-test or z-test. If you use the z-test use the P-value method.
Click here to see answer by stanbon(26259) |
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