Grade 11 - STMG / Probability 32 exercises (including 31 corrected)

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AsAsAsAsRRRRDDDDVVVV10101010999988887777 AB AAB BAB ABAB ABAB 1. Counts E.7653 An urn contains 12 white balls, 5 black balls and 8 blue balls indistinguishable by touch. Consider our universe of experience composed of the following three elementary events : A : ˇ The ball drawn is blanche ı B : ˇ The ball drawn is noire ı C : ˇ The ball drawn is bleue ı Complete the table below, to the nearest hundredth, repre-senting the probability distribution of our experiment : X A B C P ( X ) 2. Set E.7654 The table below provides an overview of daily newspaper readership in France, based on a sample of 800 people surveyed in 2005 . Every day or almost every day Once or twice a week Only-during certain periods Rarely Never Total Farmers operators 1 10 2 8 79 100 Craftsmen, shopkeepers , managers of companies 11 11 5 7 66 100 Executives 17 16 10 18 39 100 Professions inter-media 8 15 7 15 55 100 Employees 6 7 4 9 74 100 Workers (including agricultural) 4 5 3 5 83 100 Retirees 6 7 2 6 79 100 Others inactive 5 9 4 9 73 100 Total in workforce 58 80 37 77 548 800 Percentages of total 7.25 % 10 % 4.625 % In this exercise, results will be given in decimal form and rounded to the nearest 0.001 . Part A. 1 The last row of the table below represents the share of each category in relation to the total sample. Calculate the missing values in this last row. 2 Give the probability that a person chosen at random from among the executives never reads. Part B. We randomly select one person from this sample of 800 people. In this section, we note the following events : J Event : ˇ The person selected never reads ı ; O Event : ˇ the person chosen is a worker ı. 1 Calculate the probability of event J and the probability of event O . 2 Calculate the probability of event J O . 3 Calculate the probability of event J O E.7657 A random experiment involves randomly drawing a card from a deck of 32 cards. 1 Determine the probabilities of the fol-lowing events : A : ˇ The card drawn is a pique ı ; B : ˇ The card drawn is a figure ı ; C : ˇ The card drawn is noire ı ; D : ˇ The card drawn is valet ı ; 2 Determine the probabilities of the following events : a A B b A C c A B d B C e C D f C D E.7659 Below are represented the universe Ω of a random experiment and two events A and B from Ω . For each of the representations below, hatch the requested set. 3. Double-entry table https://chingmath.fr chapExoCorrec/7653 sacados/7653 chapExoCorrec/7654 sacados/7654 chapExoCorrec/7657 sacados/7657 AsAsAsAsRRRRDDDDVVVV10101010999988887777 chapExoCorrec/7659 sacados/7659 AB AAB BAB ABAB ABAB
112233445566BleuRouge E.11392 The school administration takes stock of the students enrolled in the half-board program : The school has 852 students ; In total, there are 213 students enrolled in the ˇ day stu-dent ı ; program For girls, 123 girls are enrolled in the ˇ day stu-dent ı program and 312 are enrolled in the half-board program 1 Complete the table below : Boys Filles Total Day student Half-board Total 2 A student is chosen at random from the list of students : a What is the probability that the student is a girl? b What is the probability that the student is a half-boarder? c Knowing that the student is a boy, what is the proba-bility that he is a day student? E.11427 We are interested in three sixth-grade classes at a school. Volleyball and soccer are offered as ex-tracurricular activities and together have 354 members. Here is some additional information that has been gathered : 76 girls have signed up for volleyball There are 132 members in the volleyball club. There are 238 boys. 1 Complete the table : Volleyball Soccer Total Boys Girls Total 2 We randomly select a sixth grader : a What is the probability that this student plays volley-ball? b What is the probability that this student is a girl? c Knowing that the student chosen is a boy, what is the probability that he plays soccer? E.11618 On s’intéresse à trois classes de sixièmes d’un établissement scolaire. Le Volley-ball et le Football sont proposés en activité extra-scolaire et regroupent à eux deux 354 adhérents. Voici quelques informations complémentaires recueillies: 76 filles se sont inscrites au Volley-Ball. Le Volley-Ball compte 132 adhérents. Les garçons sont au nombre de 238. 1 Compléter le tableau : Volley-ball Football Total Garçons Filles Total 2 On choisit au hasard un élève de sixième: a Quelle est la probabilité que cet élève pratique le Volley-ball ? b Quelle est la probabilité que cet élève soit une fille ? c Sachant que l’élève choisi est un garçon, quelle est la probabilité qu’il pratique le Football ? 4. Non-equiprobable situation E.11509 A random experiment con-sists in rolling two dice, red and blue, with six faces simultaneously and considering the sum ob-tained by these two dice. The dice are assumed to be perfectly balanced. 1 Describe the universe of possible outcomes. 2 a Complete the ta-ble below : https://chingmath.fr chapExoCorrec/11392 sacados/11392 chapExoCorrec/11427 sacados/11427 chapExoCorrec/11618 sacados/11618 chapExoCorrec/11509 sacados/11509 112233445566BleuRouge
EvènementsélémentairesNNNNNNNBBNNNNNNNNBBNBNNBNNBBBB1ertirage2etirage RRBRRRBRRRBBReprésentation 1 RBRRBRRRBReprésentation 2 V2F2F2F2V1V2F2F2F2F1V2F2F2F2F1V2F2F2F2F1 a Determine the probability law associated with this random experiment. 5. Choice trees E.7655 An urn contains two black balls and one white ball; the game is played with the ball being returned : i.e., once the ball has been drawn, it is returned to the urn before the next draw. Here’s a decision tree based on the drawing of two balls : 1 Taking into account the order in which the balls are drawn, what is the possible number of different draws? 2 Determine the probability of the following events : a A : ˇ The first ball drawn is blanche ı. b B : ˇ The two balls drawn are différentes ı colors. c C : ˇ The second ball is a noire ı ball. 3 Give the probabilities of the following events : a A B b A C c A C E.7662 An urn contains two red balls and one blue ball indistinguishable by touch. Using this urn, we construct two sets : We draw a first ball from the urn, then without putting it back, we draw a second ball. A first ball is drawn from the urn, its color observed and then returned to the urn. A second ball is then drawn. In both games, the game is considered won if the two balls drawn are of the same color. The two choice trees below are proposed : 1 Associate with each of the games its representation in the form of a choice tree. 2 Determine the probability of winning for each of its games. E.7658 A QCM (multiple-choice questionnaire) is proposed to students : it comprises two questions and four answers are proposed, only one of which is correct. We wish to study the percentage of success in this MCQ if the students answer it completely at random ; we then assume that the answers given to each of the questions are indepen-dent of each other. We note : F i : ˇ The answer provided to question i is fausse ı ; V i : ˇ The answer provided to the question i is vraie ı ; Here is the choice tree associated with this situation : Consider the random experiment of randomly selecting the answers to these two questions 1 Give the probability of obtaining the two correct answers. 2 Give the probability of obtaining only one correct answer. https://chingmath.fr chapExoCorrec/7655 sacados/7655 EvènementsélémentairesNNNNNNNBBNNNNNNNNBBNBNNBNNBBBB1ertirage2etirage chapExoCorrec/7662 sacados/7662 RRBRRRBRRRBBReprésentation 1 RBRRBRRRBReprésentation 2 chapExoCorrec/7658 sacados/7658 V2F2F2F2V1V2F2F2F2F1V2F2F2F2F1V2F2F2F2F1
NNNBNBNNNNBNBNNBNNBNB 123546UrneBUrneA 213214215216 122564UrneBUrneA VFFFVVFFFFVFFFFVFFFFVVFFFVVFFFFVFFFFVFFFFFVFFFVVFFFFVFFFFVFFFFFVFFFVVFFFFVFFFFVFFFFF 141414V34FV3414V34FFV341414V34FV3414V34FFF E.11510 An urn contains two black balls and one white ball; the game consists of extracting two balls from the urn without delivery: the first ball drawn will not be returned to the urn. Opposite is a choice tree repre-senting the draws in this game. 1 Taking into account the order in which the balls are drawn, what is the possible number of different draws? 2 Determine the probability of the following events : a A : ˇ The first ball drawn is blanche ı. b B : ˇ The second ball drawn is blanche ı. c C : ˇ The two balls drawn are distinctes ı colors. 3 Give the probabilities of the following events : a A B b A C c C E.11619 On considère deux urnes contenant des boules sur lesquelles est inscrit un chiffre. L’expérience aléa-toire consiste à tirer une boule au hasard dans l’urne A, puis une boule au hasard dans l’urne B et à faire la somme. 1 Voici le contenu de l’urne : On associe à cette expérience l’arbre de choix: Quelle est la probabilité d’obtenir la somme 6 ? 2 On modifie les urnes : a Construire l’arbre de choix correspondant à cette ex-périence. b Quelle est la probabilité d’obtenir la somme 7 ? 6. Probability tree E.7656 Consider a multiple-choice questionnaire consisting of 3 questions, each offering 4 answers, only one of which is correct. A random experiment is created by asking participants to answer the questions in the form at random. This situation is represented by the decision tree below : 1 Complete the probability table below : k 0 1 2 3 Probability of obtaining k correct answers Note that for each multiple-choice question, the probability of getting a correct answer is 1 4 and a wrong answer is 3 4 . We simplify the decision tree with the probability tree below : We want to find the results of question 1 using this proba- https://chingmath.fr chapExoCorrec/11510 sacados/11510 NNNBNBNNNNBNBNNBNNBNB chapExoCorrec/11619 sacados/11619 123546UrneBUrneA 213214215216 122564UrneBUrneA chapExoCorrec/7656 sacados/7656 VFFFVVFFFFVFFFFVFFFFVVFFFVVFFFFVFFFFVFFFFFVFFFVVFFFFVFFFFVFFFFFVFFFVVFFFFVFFFFVFFFFF 141414V34FV3414V34FFV341414V34FV3414V34FFF
ESESESESESESES ESESESESESESES NNNBNNNNBNNNNBNNNNBB NNNBBNNNNBBNNNNBBNNNNBBBNNNBBB bility tree : 2 a Which calculation, using the data from the tree be-low, allows us to find the probability of getting 3 cor-rect answers to Q . C . M . ? b Which calculation, using the data from the tree below, allows us to find the probability of obtaining 0 correct answers to Q . C . M . ? c Which calculation, using the data from the tree below, allows us to find the probability of obtaining 1 correct answers to Q . C . M . ? E.7670 Consider a Bernoulli scheme with pa-rameters 3 and 0.4 . 1 Complete the probability tree below : 2 How many outcomes does this random experiment have? 3 Determine the probability of obtaining 3 success. 4 a How many outcomes represent 2 success? b Determine the probability of obtaining 2 success in this random experiment. E.7671 Consider a Bernoulli scheme with pa-rameters 4 and 0.4 . 1 Complete the probability tree below : 2 How many outcomes does this random experiment have? 3 Determine the probability of obtaining 4 success. 4 a How many outcomes represent 3 success? b Determine the probability of obtaining 3 success in this random experiment. 7. Binomial law E.7681 1 There are four balls in an urn : three black balls and one white ball. Two balls are drawn successively from this urn, with delivery. The choice tree below illustrates all the elementary events in this random experiment : a Construct the associated probability tree b Note X the random variable associating the number of white balls drawn. Determine the following probabili-ties : P X =0 ; P X =2 2 In an urn are five balls : three black balls and two white balls. Two balls are drawn successively from this urn, with delivery. The choice tree below illustrates all the elementary events in this random experiment : a Construct the associated probability tree b Note X the random variable associating the number of white balls drawn. Determine the following probabili-ties : P X =1 ; P X =2 E.7682 1 a Construct a probability tree associated with a Bernoulli scheme of parameter 2 and 0.4 . b Note X a random variable following a binomial distri-bution of parameter 2 and 0.4 . Determine the follow-ing probabilities : P X =0 ; P X =1 2 a Construct a probability tree associated with a Bernoulli scheme with parameters 3 and 0.4 . b Note X a random variable following a binomial distri-bution of parameter 3 and 0.4 . Determine the follow-ing probabilities : P X =0 ; P X =1 https://chingmath.fr chapExoCorrec/7670 sacados/7670 ESESESESESESES chapExoCorrec/7671 sacados/7671 ESESESESESESES chapExoCorrec/7681 sacados/7681 NNNBNNNNBNNNNBNNNNBB NNNBBNNNNBBNNNNBBNNNNBBBNNNBBB chapExoCorrec/7682 sacados/7682
12345678910 8. Binomial law and expectation E.7720 Proposition: The expectation of a random variable X fol-lowing a binomial distribution with parameters n and p is the number n × p and is denoted by E ( X ) . Interpretation : The expectation is the observed mean value of the number of successes achieved in the Bernoulli scheme when this random experiment is performed a large number of times. 1 Consider a random variable X following the binomial dis-tribution with parameters 10 and 0 ; 3 . Determine the expectation of the random variable X . 2 Consider a random variable X following the binomial dis-tribution with parameters 24 and 0 ; 45 . Determine the expectation of the random variable X . E.7680 Five boys and three girls write their names on a piece of paper and insert it into an urn. Two pieces of paper are drawn successively from the urn, with a discount. The two draws are considered to be independent. 1 At each draw, we look to see whether the paper drawn designates a boy or a girl. Construct the probability tree related to this experiment. 2 Let X be the random variable associating with an out-come of this draw the number of girls selected. a Determine the probability distribution of X . b Calculate its mathematical expectation of E ( X ) . The result will be rounded to the nearest thousandth. E.7685 We have a well-balanced cubic die whose faces are numbered from 1 to 6 . When rolling the dice, the game is considered won if an even value is obtained. We roll the well-balanced die three times in succession and denote by X the number of times an even number was ob-tained. 1 Draw up the probability tree associated with this random experiment. 2 Give the exact value, then the value rounded to the thou-sandth of the probability P ( X =2) . 3 Give the expectation of the random variable X . 9. Binomial law and representation E.7686 Below is represented the law of the random variable X following the binomial law of parameters n =10 and p =0.3 : Give an approximate value for the following probabilities : a P X =1 b P X =3 E.7689 Below is given the representation of the law of a random variable X following a binomial distribution with parameter n =10 and p =0.7 .: Give the inequality that is verified : a P X < 5 0.5 b P X < 5 0.5 10. Binomial law and calculator E.7684 Consider a random variable X following a binomial distribution with parameters 0.2 and 20 . Questions will be answered using the calculator. Results will be rounded to the nearest 10 3 : 1 Determine the value of the following probabilities : a P X =5 b P X =9 2 Determine the value of the following probabilities : a P X 5 b P X 9 E.7807 Consider a random variable X following a binomial distribution with parameters 30 and 0.24 . Questions will be answered using the calculator. Results will be rounded to the nearest 10 3 : 1 Determine the value of the following probabilities : a P X =10 b P X =12 2 Determine the value of the following probabilities : a P X 10 b P X 18 https://chingmath.fr chapExoCorrec/7720 sacados/7720 chapExoCorrec/7680 sacados/7680 chapExoCorrec/7685 sacados/7685 chapExoCorrec/7686 sacados/7686 12345678910 chapExoCorrec/7689 sacados/7689 chapExoCorrec/7684 sacados/7684 chapExoCorrec/7807 sacados/7807
E.7687 Consider a random variable X following the binomial distribution with parameters n =5 and p =0.63 . The probability values will be rounded to three decimal places. 1 Determine the following probabilities : a P X =0 b P X =1 c P X =5 2 Give the probability of event X 4 . E.7721 For the end-of-year concert, the conservatory auditorium has 400 places reserved for parents. We’re interested in the number X of parents attending the end-of-year concert in the auditorium. The probability of each 500 parent attending the concert is estimated at 0.75 . It is assumed that X follows the binomial distribution with parameters 500 and 0.75 . 1 Calculate the expectation of X . 2 Determine the probability that the number of seats re-served for parents is sufficient. Round the result to the thousandth. E.7688 A vaccine is being tested on a popula-tion of 100 individuals. 30 of them react to this vaccine with high fevers. Each test phase is carried out on a group of 5 in-dividuals chosen at random and independently between each test. Let us note X the random variable that associates with each test phase the number of individuals who had a reaction with high fevers. 1 Justify that the random variable X follows a binomial distribution with parameters 5 and 0.3 . 2 Determine the probability that 2 individuals reacted to the vaccine with fever over a test phase. 3 Over a test phase, what is the probability that at most 4 individuals have reacted with fever. E.7690 By choosing a pupil at random from among those registered for half-board, we know that the prob-ability of the chosen pupil being satisfied with the half-board is 0.675 . We denote X the random variable equal to the number of stu-dents declaring to be satisfied with the quality of the meals. As the number of students is sufficiently large, we accept that X follows a binomial distribution with parameters 4 and 0.675 . Results will be rounded to the thousandth. 1 Calculate the probability of the event A : ˇ no student is satisfait ı. 2 Calculate the probability of the event B : ˇ all four stu-dents are satisfied with the quality of repas ı. 11. Fluctuation interval E.7852 A farmer sorts his tomatoes according to their size (calibre) . He tells his suppliers that 40 % of his tomatoes are of a calibre greater than or equal to 6 (a diameter greater than 47 mm ) . Visiting the farm, a supplier takes 30 tomatoes and observes that, among them, 10 tomatoes are of a size greater than or equal to 6 . Opposite is the cumulative distribution function of a binomial random variable with parameters 30 and 0.4 . The following results can be ex-tracted from it: P X 10 0.2915 ; P X 20 0.9991 1 a Determine the value of the smallest integer a that satisfies the condition : P X a > 0.025 b Determine the value of the smallest integer b that sat-isfies the condition : P X b 0.975 c Deduce the fluctuation interval at the threshold of 95 % of the observed frequency for the random variable X . (The limits will be rounded to 10 3 ) 2 What can be said about the supplier’s observation? E.7853 Consider a random variable X follow-ing a binomial distribution with parameters 30 and 0.32 : XB 30 ; 0.32 k 0 1 2 3 4 5 6 7 8 P ( X k ) 0 0 0.001 0.005 0.018 0.049 0.11 0.208 0.341 k 9 10 11 12 13 14 15 16 17 P ( X k ) 0.494 0.645 0.774 0.871 0.934 0.97 0.988 0.995 0.999 k 18 19 20 21 22 23 24 25 26 27 28 29 30 P ( X k ) 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Determine the smallest integers a and b such that : P X a ) > 0.025 ; P X b 0.975 2 Justify that : P a X b 0.95 3 Let F = X 30 be the random variable representing the ran-dom frequency of success. Justify that : P a 30 F b 30 0.95 12. Unclassified financial years https://chingmath.fr chapExoCorrec/7687 sacados/7687 chapExoCorrec/7721 sacados/7721 chapExoCorrec/7688 sacados/7688 chapExoCorrec/7690 sacados/7690 chapExoCorrec/7852 sacados/7852 chapExoCorrec/7853 sacados/7853
E.11859 L’exercice n’existe pas. https://chingmath.fr sacados/11859