Questions on Algebra: Probability and statistics answered by real tutors!

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 Algebra: Probability and statistics Solvers Lessons Answers archive Quiz In Depth

 Question 315893: A statistician working for the Department of Interior is constructing a systematic random sample of trees in a forest preserve. All threes have been identified and numbered with a non-invasive number attached to each bark. The statistician wishes to estimate the mean height of the trees in the forest preserve, and has calculated an appropriate sample size of n=43 trees. The 587th tree of 731 trees in the preserve was selected as the first observation in the sample. What is the number of the second observation in the sample? Click here to see answer by stanbon(57354)

 Question 316008: The mean of five numbers is 6. If one of the numbers is removed, the mean becomes 7. What is the value of the number that was removed? Click here to see answer by Edwin McCravy(8909)

 Question 316006: Bob was ranked 50th in a class of 250. What was his percentile rank? Click here to see answer by Edwin McCravy(8909)
 Question 316006: Bob was ranked 50th in a class of 250. What was his percentile rank? Click here to see answer by stanbon(57354)

 Question 316013: The median can be a more appropriate measure of central tendency than the mean if the distribution of the data is extremely skewed. A. False B. True C. It doesn’t matter, when data are skewed the mean and the median are the same D. It doesn’t matter, when data are skewed the mean, median, and mode are the same Click here to see answer by stanbon(57354)

 Question 316012: a microwave oven repairer says that the mean repair cost for damaged microwave ovens is less than \$90. You work for the repairer and want to test this claim. You find that a random sample of five microwave ovens has a mean repair cost of \$68 and a standard deviation of \$12. at alpha =0.10, do you have enough evidence to support the repairer's claim. assume the population is normally distributed Click here to see answer by stanbon(57354)

 Question 316060: a basketball player gets a basket on the average of once every 10 times he shoots. if this player shoots 6 times, what is the probability that (round answers to the 3 decimal): a) exactly 3 shots go in the basket? P of success= .10 P of not success= .90 k= 3 shots; n= 6 so: b(6,3; .10) = (6,3)(.10)^3(.90)^3 = 6!/3!3!= 20(.001)(.729)= 0.013 P(exactly 3 shots)=0.013 b) none of the shots go in? b(6,0; .10) = (6,0)(.10)^0(.90)^6 = 6!/6!0!= 1(0)(.5314)=0.531 P(exactly 0 shots)=0.531 c) less than four shots go in the basket? b(6,3;.10) + b(6,2;.10) + b(6,1;.10) + b(6,0;.10)= 0.013 + 6!/4!2!=15(.01)(.6561)=0.98415 + 6!/5!1!=6(.10)(.59049)=.354294 +.531= 0.013+0.98415+.59049+.531= .996709 P(less than 4 shots)=.997 Click here to see answer by stanbon(57354)

 Question 316063: Suppose that the time required to complete a 1040R tax form is normally distributed with a mean of minutes and a standard deviation of minutes. What proportion of 1040R tax forms will be completed in less than minutes? Round your answer to at least four decimal places. Click here to see answer by stanbon(57354)

 Question 316030: find the z score that has 28.1% of the distribution's area to the left Click here to see answer by stanbon(57354)

 Question 316016: In a study of elephants a researcher wishes to determine the average weight of a certain subspecies of elephants. From previous studies, the standard deviation of the weights of elephants in this subspecies is known to be 1500 pounds. How many elephants does the researcher need to weigh so that he can be 80% confident that the average weight of elephants in his sample is within 350 pounds of the true average weight for this subspecies? A. 31 B. 39 C. 50 D. 166 Click here to see answer by stanbon(57354)

 Question 316002: Assume the body temperatures of healthy adults are normally distributed with a mean of 98.20 °F and a standard deviation of 0.62 °F (based on data from the University of Maryland researchers). a. If you have a body temperature of 99.00 °F, what is your percentile score? b. Convert 99.00 °F to a standard score (or a z-score). c. Is a body temperature of 99.00 °F unusual? Why or why not? d. Fifty adults are randomly selected. What is the likelihood that the mean of their body temperatures is 97.98 °F or lower? e. A person’s body temperature is found to be 101.00 °F. Is the result unusual? Why or why not? What should you conclude? Click here to see answer by stanbon(57354)

 Question 316067: last question on my homework over continuous distribution and my life time has been shortened by this question. please help. A flight arrives at a random time, uniformly distributed between 6:00 pm and 6:30 pm. Find the probability that the flight arrives (a) before 6:10 (b) between 6:15 and 6:25 (c) after 6:20 (d) before 6:20 (e) between 6:05 and 6:25 (f) after 6:10 Click here to see answer by scott8148(6628)

 Question 316101: The mean of five numbers is 6. If one of the numbers is removed, the mean becomes 7. What is the value of the number that was removed? Click here to see answer by scott8148(6628)

 Question 316100: Tim was ranked 50th in a class of 250. What was his percentile rank? Click here to see answer by nerdybill(6959)

 Question 316141: A laboratory tested 70 chicken eggs and found that the mean amount of cholesterol was 228 milligrams with s = 12 milligrams. Construct a 95 percent confidence interval for the true mean cholesterol content, μ, of all such eggs. Click here to see answer by stanbon(57354)

 Question 316140: What is the critical value of that corresponds to a degree of confidence of 91%? Click here to see answer by stanbon(57354)

 Question 316103: Suppose there were “x” students in a class who scored 100 and “y” students who scored 50. Write an algebraic expression for the mean in terms of “x” and “y”. Click here to see answer by stanbon(57354)

 Question 296034: New York has a lottery game called Quick Draw,in which the player can pick anywhere from 1 up to 10numbers from 1 to 80. The computer then picks 20 num-bers, and how much you win is based on how many of your numbers match the computer’s. For simplicity, we will onlyconsider the two cases in which you pick 4 or 5 numbers.The payoffs for each dollar that you bet are given in the table below. How Many Numbers Match theComputer’s Numbers 0 1 2 3 4 5 you pick 4 0 0 1 5 55 you pick 5 0 0 0 2 20 300 a. According to the Quick Draw playing card, the “OverallChances of Winning” when you pick 4 are “1:3.86,”while the chances when you pick 5 are “1:10.34.” Verifythese figures. b. Find the expected value when you pick 4 and when youpick 5, betting \$1 each time. c. Based on your results from parts a and b, are you betteroff picking 4 numbers or picking 5? Explain your rea-soning. Click here to see answer by reid2(1)

 Question 316249: A data set consists of a set of numerical values. Which, if any, of the following statements could be correct? a. There is no mode b. There are two modes c. There are three modes Click here to see answer by Edwin McCravy(8909)

 Question 316248: a jar contains nine marbles numbered 1-9. two marbles are randomly selected one at a time without replacement. what is the probability that a. 1 is selected first and then 9 b. the sum of the numbers selected is 4? c. the sum of the numbers selected is 5? Click here to see answer by Fombitz(13828)

 Question 316278: Struggling with expectation, can you help? The number of failures of a computer system in a week of operation has the following pmf: No of failures 0 1 2 3 4 5 6 Probability 0.18 0.28 0.25 0.18 0.06 0.04 0.01 (a) Find the expected number of failures in a week. (b) Find the variance of the number of failures in a week. Click here to see answer by Fombitz(13828)

 Question 316275: Trying to get my head around normal distribution, please help. The time spent by students working on a project is a normal random variable with parameters m = 12 hours and s = 4 hours. Compute the probability that (a) the amount of time spent on the project is less than 14 hours. (b) the amount of time spent on the project is greater than 8 hours. Click here to see answer by Fombitz(13828)

 Question 316167: In a class of fewer than 30 students, two received a "B" on a math test, 1/7 of the class received a "C", 1/2 received a "D", and 1/4 of the class failed the exam. how many students received an "A" Click here to see answer by moshiz08(60)

 Question 316335: A landscape contractor bids on jobs where he can make \$3000 profit. The probability of getting 1, 2, 3, 4, jobs are 0.2, 0.3, 0.4, 0.1 respectfully. Find the contractor's expected profit per month Click here to see answer by Fombitz(13828)

 Question 316451: if you make guesses for four multiple choice test questions (each with 5 possible answers), what is the probability of getting at least one correct? Click here to see answer by moshiz08(60)

 Question 315902: How many ways can you select a different meal if the menu offers a choice of 4 appetizers, 9 entrees, 3 desserts and 12 drinks? Thanks in advance! Click here to see answer by moshiz08(60)

 Question 316472: A target consists of concentric circles of radii 1 cm, 2 cm and 3 cm. The innermost circle is colored red, the middle ring is colored white, and the outer ring is colored blue. If a point is chosen at random on the target, what is the probability that it lies in the blue region? Express your answer as a common fraction. Click here to see answer by Fombitz(13828)

 Question 316509: The XYZ Company tested a new product and found its lifetime to be normally distributed, with a mean life of 146 days and a standard deviation of 19.5 days. What is the probability that a product selected at random will last longer than 166 days? Answer Click here to see answer by Fombitz(13828)

 Question 316508: A normal distribution has a mean of 23.5 and a standard deviation of 3.61. Find the data value corresponding to a z-score value of 1.32. Round to the nearest hundredth. Click here to see answer by Fombitz(13828)

 Question 316450: if a couple plans to have 6 children, what is the probability that they will have at least one girl? Click here to see answer by Fombitz(13828)

 Question 316511: you roll 2 dice. whats the probability that the sum of the dice is even or the sum of the dice is less than 6? Click here to see answer by Fombitz(13828)

 Question 316488: find the median for the given data. the ages (years) of th eight passengers on a bus are 6 1 29 18 26 43 40 30. Click here to see answer by Fombitz(13828)

 Question 316505: Consider the following table of test scores. Test Score 90 80 70 60 50 Frequency 3 5 8 3 2 Find the median of this data. Click here to see answer by Fombitz(13828)

 Question 316545: I am completely lost on this question: The next state lottery will have the following payoffs possible with their associated probabilities. Payoff Probability \$2.00 0.0500 \$25.00 0.0100 \$100.00 0.0050 \$500.00 0.0010 \$5,000.00 0.0005 \$10,000.00 0.0001 You buy a single ticket. 3. Referring to Table 4-7, if you have a winning ticket, the probability that you win at least \$100.00 is Any help would be appreciated. Click here to see answer by Fombitz(13828)

 Question 316540: A student takes a 20-question, true/false exam and guesses on each question. fkind the probability of passing if the lowest passing grade is 15 correct out of 20. How do I compute using the binomial distribution formula: P(X) = n! *p _______ (n-x)!X! Click here to see answer by solver91311(16885)

 Question 316598: The XYZ Company tested a new product and found its lifetime to be normally distributed, with a mean life of 146 days and a standard deviation of 19.5 days. what is the probability that a product will last between 154 and 180 days? Click here to see answer by stanbon(57354)

 Question 316597: The diameter of a pipe is normally distributed with a mean of 0.4 inch and a variance of 0.0004. What is the probability that the diameter of a randomly selected pipe will exceed 0.44 inch? Express your answer as a percen to two decimal places. Click here to see answer by Fombitz(13828)

 Question 316639: Dr.Barton has been teaching basic statistics for many years. He knows that 80 percent of the students will complete the assigned problems. He has also determined that among those who do complete the assignment, 90 percent will pass the course. Among thise students who do not complete their assiggments, 50 percent will pass. Mike Fishman took statistics last semester from Dr. Barton and received a passing grade. What is the probability he completed the assignments? This is what I got. Is it right? P(a)=0.80 P(p|a)=0.90 so .8*.9= 0.72 Click here to see answer by stanbon(57354)

 Question 316280: Not to sure how to solve this one, any ideas? A keyword search program lists the files that contain a given keyword. If it runs through 200 files, and each file contains the keyword with probability 0.25, independently of other files, compute the probability that least 50 files will be listed. Click here to see answer by stanbon(57354)

 Question 316650: five students were given a page of problems with the instructions to solve as many as they could in one hour. Five students solved the following number of problems: 12, 10, 8, 6 and 4. what is the arithmatic mean number of minutes required per problem? Click here to see answer by Fombitz(13828)

 Question 316654: A tire manufacturer advertises that "the average life of our new all-season radial tire is 50,000 miles. An immediate adjustment will be made on any tire that does not last 50,000 miles." You purchased four of these tires. What is the probability that all four tires will last more than 50,000 miles? Click here to see answer by solver91311(16885)

 Question 316685: in a shipment of 15 sets of golf clubs, 3 are left handed. if 4 sets of golf clubs are selected, what is the proability that exactily 1 is left handed, at least 1 is left-handed, no more than 2 are left handed and what is the eman number of left handed sets of golf clubs that you would expect to find in th esmaple of 4 sets of golf clubs Click here to see answer by stanbon(57354)

 Question 316506: The table shows the salaries for several employees. Which measure of central tendency is most representative of the salaries? Employees Salaries President \$152,000 Vice President \$120,500 Manager \$89,000 Supervisors \$53,000 Workers \$31,000 Click here to see answer by ryanb(1)

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