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12 . If a normally distributed random variable has µ = 0 and σ = 1, then 97.5% of the population values lie above:

  1. –1.96.
  2. 1.96.
  3. 1.
  4. –1.


Use the following information to answer the next three exercises. The amount of money a customer spends in one trip to the supermarket is known to have an exponential distribution. Suppose the average amount of money a customer spends in one trip to the supermarket is $72.

13 . What is the probability that one customer spends less than $72 in one trip to the supermarket?

  1. 0.6321
  2. 0.5000
  3. 0.3714
  4. 1

14 . How much money altogether would you expect the next five customers to spend in one trip to the supermarket (in dollars)?

  1. 72
  2. 72 2 5
  3. 5184
  4. 360

15 . If you want to find the probability that the mean amount of money 50 customers spend in one trip to the supermarket is less than $60, the distribution to use is:

  1. N (72, 72)
  2. N ( 72 , 72 50 )
  3. Exp (72)
  4. E x p ( 1 72 )


Use the following information to answer the next three exercises: The amount of time it takes a fourth grader to carry out the trash is uniformly distributed in the interval from one to ten minutes.

16 . What is the probability that a randomly chosen fourth grader takes more than seven minutes to take out the trash?

  1. 3 9
  2. 7 9
  3. 3 10
  4. 7 10

17 . Which graph best shows the probability that a randomly chosen fourth grader takes more than six minutes to take out the trash given that he or she has already taken more than three minutes?

There are 4 uniform distribution graphs. Graph (a) shows a Uniform Distribution from x = 2 to x =  9 with a height of 1/7. The area between x = 6 and x = 9 is shaded. Graph (b) shows a Uniform Distribution from x = 1 to x =  9 with a height of 1/9. The area between x = 6 and x = 9 is shaded. Graph (c) shows a Uniform Distribution from x = 3 to x =  9 with a height of 1/9. The area between x = 6 and x = 9 is shaded. Graph (d) shows a Uniform Distribution from x = 3 to x =  9 with a height of 1/7. The area between x = 6 and x = 9 is shaded.

18 . We should expect a fourth grader to take how many minutes to take out the trash?

  1. 4.5
  2. 5.5
  3. 5
  4. 10


Use the following information to answer the next three exercises: At the beginning of the quarter, the amount of time a student waits in line at the campus cafeteria is normally distributed with a mean of five minutes and a standard deviation of 1.5 minutes.

19 . What is the 90 th percentile of waiting times (in minutes)?

  1. 1.28
  2. 90
  3. 7.47
  4. 6.92

20 . The median waiting time (in minutes) for one student is:

  1. 5.
  2. 50.
  3. 2.5.
  4. 1.5.

21 . Find the probability that the average wait time for ten students is at most 5.5 minutes.

  1. 0.6301
  2. 0.8541
  3. 0.3694
  4. 0.1459

22 . A sample of 80 software engineers in Silicon Valley is taken and it is found that 20% of them earn approximately $50,000 per year. A point estimate for the true proportion of engineers in Silicon Valley who earn $50,000 per year is:

  1. 16.
  2. 0.2.
  3. 1.
  4. 0.95.

23 . If P ( Z < z α ) = 0.1587 where Z ~ N (0, 1), then α is equal to:

  1. –1.
  2. 0.1587.
  3. 0.8413.
  4. 1.

24 . A professor tested 35 students to determine their entering skills. At the end of the term, after completing the course, the same test was administered to the same 35 students to study their improvement. This would be a test of:

  1. independent groups.
  2. two proportions.
  3. matched pairs, dependent groups.
  4. exclusive groups.

A math exam was given to all the third grade children attending ABC School. Two random samples of scores were taken.

n x ¯ s
Boys 55 82 5
Girls 60 86 7

25 . Which of the following correctly describes the results of a hypothesis test of the claim, “There is a difference between the mean scores obtained by third grade girls and boys at the 5% level of significance”?

  1. Do not reject H 0 . There is insufficient evidence to conclude that there is a difference in the mean scores.
  2. Do not reject H 0 . There is sufficient evidence to conclude that there is a difference in the mean scores.
  3. Reject H 0 . There is insufficient evidence to conclude that there is no difference in the mean scores.
  4. Reject H 0 . There is sufficient evidence to conclude that there is a difference in the mean scores.

Questions & Answers

If a random variable X takes only two values -2 and 1 such that 2 P[X=- 2]=P[X=1]=P, then find variance of x.
Dikshita Reply
2.5
Anirban
the mean of random variable following binomial distribution is 10. the numbers of trails are 30. What the approximate value of variance?
AMIT Reply
what is chis square
Remelyn Reply
A chi-square (χ2) statistic is a test that measures how a model compares to actual observed data.
kalim
descriptive statistics basic
Sangeetha
Hi Friends
Sangeetha
tamil people yaaraavathu irukkingala
Sangeetha
what is the median of the following set of number:3,3,3,4,5,6,7,8,8,9?
Sur Reply
3
Mbemah
5.6
Alekya
(5+6)/2=5.5555.......=5.6
Lyrical
(5+6)/2=5.5 that is the median
moniba
hi friends am new here, hope am welcome
nathan
hi friends am new here, hope am welcome
nathan
1.5
nathan
differences between Intervals and Ratio measurement scales
VIP Reply
interval is the distinct from a starting point to the peak of a certain distance
Mbemah
the taking of a certain range accurately in a divisional way
Mbemah
i need the solution for exercise sums
Siva Reply
descriptive statistics sums I need
Sangeetha
statistics discovered?
Kaleem Reply
internet
Kamranali
dev OS
Virendra
searching for motivation to learn stat
Nija
purpose of of statistics
mukesh
ya..
mukesh
tamil people yaraavathu inrukkingala
Sangeetha
Odisha ru kau bhai mane achha?
Hemanta
I want to learn my MSC by statistics who can help me ?
Abebe
@Avirup interest person
Abebe
good morning
Sangeetha
Dr good morning
mukhtar
in statistical inferences we use population parameter to infer sample statistics
anupama Reply
Yes
lukman
how do we calculate decile
Drix Reply
how do we calculate class boundaries
Syed
The lower class boundary is found by subtracting 0.5 units from the lowerclass limit and the upper class boundary is found by adding 0.5 units to the upper class limit. The difference between the upper and lowerboundaries of any class.
Ekene
The lower class boundary is found by subtracting 0.5 units from the lowerclass limit and the upper class boundary is found by adding 0.5 units to the upper class limit. The difference between the upper and lowerboundaries of any class.
Ekene
complete definition plz
Zarifa Reply
what are the advantages and disadvantages of primary and secondary data
Elisha Reply
the average increase for all NASDAQ stocks is the
Technical Reply
formula of poisson probability distribution
Ch Reply
frequency distribution table
Ali Reply
Giveanswer
Girma
sum of dots when 2 dice are rolled is
Babra Reply

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Source:  OpenStax, Introductory statistics. OpenStax CNX. May 06, 2016 Download for free at http://legacy.cnx.org/content/col11562/1.18
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