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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

what is standard deviation?
Jawed Reply
It is the measure of the variation of certain values from the Mean (Center) of a frequency distribution of sample values for a particular Variable.
Dominic
Yeah....the simplest one
IRFAN
what is the number of x
Godgift Reply
10
Elicia
Javed Arif
Jawed
how will you know if a group of data set is a sample or population
Kingsley Reply
population is the whole set and the sample is the subset of population.
umair
if the data set is drawn out of a larger set it is a sample and if it is itself the whole complete set it can be treated as population.
Bhavika
hello everyone if I have the data set which contains measurements of each part during 10 years, may I say that it's the population or it's still a sample because it doesn't contain my measurements in the future? thanks
Alexander
Pls I hv a problem on t test is there anyone who can help?
Peggy
What's your problem Peggy Abang
Dominic
Bhavika is right
Dominic
what is the problem peggy?
Bhavika
hi
Sandeep
Hello
adeagbo
hi
Bhavika
hii Bhavika
Dar
Hi eny population has a special definition. if that data set had all of characteristics of definition, that is population. otherwise that is a sample
Hoshyar
three coins are tossed. find the probability of no head
Kanwal Reply
three coins are tossed consecutively or what ?
umair
p(getting no head)=1/8
umair
or .125 is the probability of getting no head when 3 coins are tossed
umair
🤣🤣🤣
Simone
what is two tailed test
Umar Reply
if the diameter will be greater than 3 cm then the bullet will not fit in the barrel of the gun so you are bothered for both the sides.
umair
in this test you are worried on both the ends
umair
lets say you are designing a bullet for thw gun od diameter equals 3cm.if the diameter of the bullet is less than 3 cm then you wont be able to shoot it
umair
In order to apply weddles rule for numerical integration what is minimum number of ordinates
Anjali Reply
excuse me?
Gabriel
why?
Tade
didn't understand the question though.
Gabriel
which question? ?
Tade
We have rules of numerical integration like Trapezoidal rule, Simpson's 1/3 and 3/8 rules, Boole's rule and Weddle rule for n =1,2,3,4 and 6 but for n=5?
John
geometric mean of two numbers 4 and 16 is:
iphone Reply
10
umair
really
iphone
quartile deviation of 8 8 8 is:
iphone
sorry 8 is the geometric mean of 4,16
umair
quartile deviation of 8 8 8 is
iphone
can you please expalin the whole question ?
umair
mcq
iphone
h
iphone
can you please post the picture of that ?
umair
how
iphone
hello
John
10 now
John
how to find out the value
srijth Reply
can you be more specific ?
umair
yes
KrishnaReddy
what is the difference between inferential and descriptive statistics
Eze Reply
descriptive statistics gives you the result on the the data like you can calculate various things like variance,mean,median etc. however, inferential stats is involved in prediction of future trends using the previous stored data.
umair
if you need more help i am up for the help.
umair
Thanks a lot
Anjali
Inferential Statistics involves drawing conclusions on a population based on analysis of a sample. Descriptive statistics summarises or describes your current data as numerical calculations or graphs.
fred
my pleasure😊. Helping others offers me satisfaction 😊
umair
for poisson distribution mean............variance.
mehul Reply
both are equal to mu
Faizan
mean=variance
Faizan
what is a variable
Bonolo Reply
something that changes
Festus
why we only calculate 4 moment of mean? asked in papers.
Faizan Reply
why we only 4 moment of mean ? asked in BA exam
Faizan
Good evening, can you please help me by sharing regression and correlation analysis notes....thank you in advance
Refiloe Reply
Hello, can you please share the possible questions that are likely to be examined under the topic: regression and correlation analysis.
Refiloe
for normal distribution mean is 2 & variance is 4 find mu 4?
Faizan Reply
repeat quastion again
Yusuf
find mu 4. it can be wrong but want to prove how.
Faizan
for a normal distribution if mu 4 is 12 then find mu 3?
Faizan Reply
Question hi wrong ha
Tahir
ye BA mcqs me aya he teen he. 2dafa aya he
Faizan
if X is normally distributed. (n,b). then its mean deviation is?
Faizan
The answer is zero, because all odd ordered central moments of a normal distribution are Zero.
nikita
which question is zero
Faizan
sorry it is (5,16) in place of (n,b)
Faizan
I got. thanks. it is zero.
Faizan
a random variable having binomial distribution is?
Bokaho

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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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