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Tutors Answer Your Questions about Probability-and-statistics (FREE)
Question 185842This question is from textbook 
: Can you please help thank you
1 If a court acquits every defendant, they will never commit a Type I error.
A)
True
B)
False
2 The probability of rejecting a true null hypothesis increases as the sample size increases.
A)
True
B)
False
3 For a given level of significance, the critical value of Student's t increases as n increases.
A)
True
B)
False
4 In a two-tailed hypothesis test with α = .05, a test statistic of t = 1.813 with d.f. = 15 leads one to reject the null hypothesis of a statistical test.
A)
True
B)
False
5 The power of a test is the probability that the test will reject a false null hypothesis.
A)
True
B)
False
6 The height of the power curve shows the probability of accepting a true null hypothesis
A)
True
B)
False
7 Which is not true of p-values?
A)
When they are small, we want to reject Ho.
B)
They must be specified before the sample is taken.
C)
They show the chance of Type I error if we reject Ho.
D)
They do not require α to be specified a priori.
Use the following scenario to answer questions 8 to 10.
Dullco Manufacturing claims that its alkaline batteries last forty hours on average in a certain type of portable CD player. Tests on a random sample of 18 batteries showed a mean battery life of 37.8 hours with a standard deviation of 5.4 hours.
8 The test statistic is
A)
-1.980
B)
-1.728
C)
-2.101
D)
-1.960
9 In determining the p-value for reporting the study's findings, which of the following is true?
A)
The p-value is less than .05.
B)
The p-value is equal to .05.
C)
The p-value is greater than .05.
D)
The p-value cannot be determined without specifying α.
10 In a left-tailed test at α = .05 we would
A)
comfortably reject the claim.
B)
comfortably accept the claim.
C)
feel uncomfortable with either decision (too close).
D)
switch to alpha of 0.01 for a more powerful test.
This question is from textbook
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Question 185819This question is from textbook doane-Seward
: Please I am new to statistic and i need help with the questions below can you please help me. the questions is
A 20- minute consumer survey mailed to 500 adults aged 25-34 included a $5 Starbucks gift certificate. The same survey was mailed to 500 adults aged 25-34 without the gift certificate. There were 65 responses from the first group and 45 from the second group. (a) Perform a two-tailed test comparing the responses rates (proportions) at a=.05. (b) from a confidence interval for the difference of proportions, without pooling the samples. Does it include zero?
Are womans feet getting bigger? Retailers in the last 20 years have had to increase their stock of larger sizes. Wal-Mart Stores, Inc., and Payless Shoe Source, Inc., have been aggressive in stocking larger sizes, and Nordstroms reports that its larger sizes typically sell out first, assuming equal variances, at a=.025, do these random shoe size samples of 12 randomly chosen women in each age group show that womens shoe sizes have increase? (See The Wall Street Journal, July 17, 2004.) Shoe Size
Born in 1980: 8 7.5 8.5 8.5 8 7.5 9.5 7.5 8 8 8.5 9
Born in 1960: 8.5 7.5 8 8 7.5 7.5 7.5 8 7 8 7 8
Block buster is testing a new policy of waiving all late fees on DVD rentals using a sample of 10 randomly chosen customers. (a) At a= .10, does the data show that the mean number of monthly rentals has increased? (b) is the decision close? (C Are you convinced?
Customer
Customer No Late Fee Late Fee
1 14 10
2 12 7
3 14 10
4 13 13
5 10 9
6 13 14
7 12 12
8 10 7
9 13 13
10 13 9
This question is from textbook doane-Seward
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Question 185977: Rewa asked 150 randomly chosen students what programmes they had watched the previous night
on television. Shortland Street was watched by 90 students, 50 students had watched NZ Idol, and
30 had watched both.
What is the probability that a randomly chosen student had watched neither Shortland Street nor
NZ Idol the previous night?
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Question 185999: This is a college stats problem-
In testing a new drug, researchers found that 5% of all patients using it will have a mild side effect. A random sample of 11 patients using the drug is selected. Find the probability that:
a) exactly 2 will have this mild side effect
I can't figure this part out- 11/9*2???
b) at least 1 will have this mild side effect
1 - (0.95^11) = 0.4312
Thanks
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Question 185970: use the "68-95-99.7 rule" to estimate the area lying between values x=1,100 and x=2,600 under the normal curve that has mean 2,100 and standard deviation 500. Use the "Rule" and solve not using a calculator.
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Question 185968: you trace a frequency histogram of a distribution of x-values onto a uniformly thick sheet of plastic and cut it out. Which statements A,B,C, or D is true?
A. statements 1 and 3 are correct
b. statements 1 and 4 are correct
c. statements 2 and 3 are correct
d. statements 2 and 4 are correct
1. if the data are right-skewed, the median will be located to the right of the mean
2. if the data are right-skewed, the mean will be located to the right of the median
3. the median is the value of x at which the histogram balances, and the mean is the value of x that is larger than (or equal to) half of the x-values.
4. the mean is the value of x at which the histogram balances, and the median is the value of x that is larger than (or equal to) half of the x-values.
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Question 186034: More on Predicted Probabilities
14.A version of Intro the Pound uses a number cube. Then, spin the spinner. Multiply.
a)What are the possible products when you multiply the results of the spinner and the number cube?
b)What is the predicted probability ogf getting each product?
Can anyone please help me at this question reallyyyyyy really dont get this question....thank you veryyyyyyyyy much
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Question 186049: Mr. Alim's science class launched a toy rocket from ground level with an initial upward velociy of 60 feet per second. The height h of the rocket in feet above the ground after t seconds is modeled by the equation h=60t-(16t)(16t). How long was the rocket in the air before it returned to the ground?
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Question 186032: More on predicted Probablities
1.What is the probability of tossing twoheads if you use two pennies?
Is the probability of tossing two heads the same or different if you use a quarter and a dime? Explain.
Can you please help me..i dont understand it>?
thank you sooooooooooooooooooooooooo much
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Question 186155This question is from textbook doana and seward
: Can you please help me with solving the question below please
9.54
Faced with rising fax costs, a firm issued a guideline that transmissions of 10 pages or more should be sent by 2-day mail instead. Exceptions are allowed, but they want the average to be 10 or below. The firm examined 35 randomly chosen fax transmissions during the next year, yielding a sample mean of 14.44 with a standard deviation of 4.45 pages. (a) At the .01 level of significance, is the true mean greater than 10? (b) Use Excel to find the right-tail p-value.
9.56
A coin was flipped 60 times and came up heads 38 times. (a) At the .10 level of significance, is the coin biased toward heads? Show your decision rule and calculations. (b) Calculate a p-value and interpret it.
9.62
The Web-based company Oh Baby! Gifts has a goal of processing 95 percent of its orders on the same day they are received. If 485 out of the next 500 orders are processed on the same day, would this prove that they are exceeding their goal, using α = .025? (See story. news. yahoo. comaccessed June 25, 2004.)
9.64
An auditor reviewed 25 oral surgery insurance claims from a particular surgical office, determining that the mean out-of-pocket patient billing above the reimbursed amount was $275.66 with a standard deviation of $78.11. (a) At the 5 percent level of significance, does this sample prove a violation of the guideline that the average patient should pay no more than $250 out-of-pocket? State your hypotheses and decision rule. (b) Is this a close decision?
This question is from textbook doana and seward
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Question 186298: how do i solve this In testing a new drug, researchers found that 5% of all patients using it will have a mild side effect. A random sample of 11 patients using the drug is selected. Find the probability that:
a) exactly two will have this mild side effect
b) at least one will have this mild side effect.
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Question 186305: X has a normal distribution with a mean of 75.0 and a standard deviation of 2.5. Find the following probabilities:
a) P(x < 70.0) i did 70-75/2.5= -2 but dont know what's next
b) P(72.5 < x < 80.0) not sure
c) P(x >82.5) 75-82.5/2.5= -3 i use table to look for z
3=0.3821 p(z<-3)=0.3821
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Question 186258: Hello, Iam having some trouble with my statistics homework, please I hope some one can help me.I have two questions:
: Confidence Intervals for the Mean (Small Samples)
1) An experimental egg farm is raising chickens to produce low cholesterol eggs. A lab tested 25 randomly selected eggs and found that the mean amount of cholesterol was 190 mg. The sample standard deviation was found to be s = 18.0 mg on this group. Assume that the population is normally distributed.
a. Find the margin of error for a 95% confidence interval. Round your answer to the nearest tenths.
b.Find a 95% confidence interval for the mean cholesterol content for all experimental eggs. Assume that the population is normally distributed.
Confidence Intervals for Population Proportions
2) The new Twinkle bulb is being developed to last more than 1000 hours. A random sample of 100 of these new bulbs is selected from the production line. It was found that 75 lasted more than 1000 hours. Find the point estimate for the population proportion, the margin of error for a 95% confidence interval and then construct to the 95% confidence interval for the population proportion p.
a. Find the margin of error E.
b.Construct a 95% confidence interval for the population proportion p of all Twinkle bulbs.
I would like to thank you in advance for all your help and using your time to help me.
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Question 186197This question is from textbook doana and seward
: Can some please help thank you
In a bumper test, three types of autos were deliberately crashed into a barrier at 5 mph, and the resulting damage (in dollars) was estimated five test vehicles of each type were crashed, with the results shown below. Research question: Are the mean crash damages the same for these three vehicles? Crash1
Crash Damage ($)
Goliath Varmint Weasel
1,600 1,290 1,090
760 1,400 2,100
880 1,390 1,830
1,950 1,850 1,250
1,220 950 1,920
This question is from textbook doana and seward
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Question 186394: Research at the University of Toledo indicates that 50 percent of the students change their major area of study after their first year in a program. A random sample of 100 students in the College of Business revealed that 48 had changed their major area of study after their first year of the program. Has there been a significant decrease in the proportion of students who change their major after the first year in this program? Test at the .05 level of significance.
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Question 186165: 106) you have 3 cards: an ace,a king,a queen. A friend shuffles the cards, selects two of them at random, and discards the third. you ask your friend to show you a picture card, and she turns over the king.
A) what is the probabilty that she also has the king?
_______________________________________________________________________________
-consider a six sided die that has 1 dot on one side, 2 dots in two sides and dots on 3 dots on three sides.
-- if the side is rolled twice determine the probabilty of rolling.
108) two 3's
110) an odd number greater then 1
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Question 186937: I need help in statistics. Can someone help me with this? Thank you!
A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech Pages Plus Yellow Pages. On each page, the mean area devoted to display ads was measured (a display ad is a large block of multicolored illustrations, maps, and text). The data (in
square millimeters) are shown below:
0 260 356 403 536 0 268 369 428 536
268 396 469 536 162 338 403 536 536 130
(a) Construct a 95 percent confidence interval for the true mean.
(b) Why might normality be an issue here?
(c) What sample size would be needed to obtain an error of }10 square millimeters with 99 percent confidence?
(d) If this is not a reasonable requirement, suggest one that is.
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Question 186955: A spinner is divde into 6 segments, each labled with a different positive integer. The theoretical probabilityof spinning a number less than 8 is 1. The theoretical probability of spinning a multiple of 3 is 1/3, a multiple of 4 is 1/6, and an odd number is 2/3. give me the numbers on the spinner
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Question 186936: I need help with my statistics class. Can someone please help me with this? Thanks
As an experiment, a self-confessed connoisseur of cheap popcorn carefully counted 773 kernels and put them in a popper. After popping, the unpopped kernels were counted. There were 86.
(a) Construct a 90 percent confidence interval for the proportion of all kernels that would not pop.
(b) Check the normality assumption.
(c) Try the Very Quick Rule.
Does it work well here?
Why, or why not?
(d) Why might this sample not be typical?
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Question 186912: The employees of Jones Construction Co. are allowed a 30-minute lunch break. The union wants to know if the employees are actually taking breaks that are less than 30 minutes. The union decides to record the times taken for the next 25 breaks taken at the site. The data are summarized as follows:
sample mean = 28.84 min
sample standard deviation = 5.145 min
a. State the appropriate null and alternative hypotheses.
b. Calculate the test statistic.
c. At = 0.05, should the union reject the null hypothesis?
d. What conclusion can the union present to the owner
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Question 186859This question is from textbook Doane and Seward
: I need help can some please help me with the following question below please
1.In a two-sample test of means for independent samples, the equal sign always appears in
A)
The null hypothesis.
B)
The alternate hypothesis.
C)
The upper tail of the test statistic.
D)
None of the above.
2. In a two-sample test of means for independent samples, we use the z distribution when
A)
The population standard deviations are equal.
B)
Both populations have at least 4000 observations.
C)
Both population standard deviations are known.
D)
nB and n(1-B) are both greater than 5.
3. Which of the following is a requirement for a two-sample test of proportions.
A)
The population standard deviations are equal.
B)
Both populations are positively skewed.
C)
Both samples are at least 30.
D)
nB and n(1-B) are both greater than 5.
4.A random sample of 10 observations is selected from the first normal population and 8 from the second normal population. For a one-tailed test of hypothesis (.01 significance level) to determine if there is a difference in the population means, the degrees of freedom are
A)
18
B)
17
C)
16
D)
None of the above
5.A random sample of 10 observations is selected from the first normal population and 8 from the second normal population. For a one-tailed test of hypothesis (.01 significance level) to determine if there is a difference in the population means, the critical value(s) are
A)
2.552
B)
-2.921, 2.921
C)
-2.583, 2.583
D)
None of the above
6. Which of the following is not a requirement for the two-sample test of means for independent samples observations?
A)
Normal populations
B)
Equal population standard deviations
C)
Equal sample sizes
D)
All of the above are required.
7. To conduct a test of means for two independent samples which of the following are always required?
A)
At least one of the samples must have 30 observations.
B)
Both samples must have 30 observations.
C)
np and n (1 - p) must be 5.
D)
None of the above.
8.To conduct a test of hypothesis for dependent samples we assume that
A)
The distribution of the difference between the paired observations follows the normal distribution.
B)
Both samples are at least 30.
C)
The samples are unrelated.
D)
All of the above.
9.When conducting a test of hypothesis for the dependent samples
A)
We should have at least 30 pairs.
B)
The significance level is more than .05.
C)
The p-value is more than .10.
D)
None of the above
10.Which of the following is not necessary to determine a p-value?
A)
Knowledge of whether the test is one-tailed or two-tailed.
B)
The value of the test statistic.
C)
The level of significance.
D)
All of the above.
This question is from textbook Doane and Seward
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Question 186797: Please help me with these questions. Thanks
1. If the alternate hypothesis states that does not equal 4,000, what is the rejection region for the hypothesis test? A. Both tails
B. Lower or left tail
C. Upper or right tail
D. Center
E. None of the above
2. If 20 out of 50 students sampled live in a college dormitory, what is the estimated proportion of students at the University living in a dormitory?
A. 0.20
B. 0.40
C. 0.50
D. 0.60
E. None of the above
3. Suppose we are testing the difference between two proportions at the 0.05 level of significance. If the computed z is 1.07, what is our decision?
A. Reject the null hypothesis
B. Do not reject the null hypothesis
C. Take a larger sample
D. Reserve judgment
E. None of the above
The mean gross annual incomes of certified tack welders are normally distributed with the mean of $20,000 and a standard deviation of $2,000. The ship building association wishes to find out whether their tack welders earn more or less than $20,000 annually. The alternate hypothesis is that the mean is not $20,000.
4. If the level of significance is 0.10, what is the decision rule?
A. Do no reject the null hypothesis if computed z lies between 1.65 and +1.65; otherwise, reject it
B.. Do not reject the null hypothesis if computed z is greater than 1.65; otherwise, reject it
C. Do not reject the null hypothesis if computed z lies between
1.96 and +1.96; otherwise, reject it
D. Reject the null hypothesis if computed z is below 1.96; otherwise, reject it
E. None of the above
5. Which of the following is the alternate hypothesis?
A. $20,000
B. $20,000
C. < $20,000
D. = $20,000
E. = $20,000
6. If the level of significance is 0.10, what is the critical value?
A. 1.65
B. 2.58
C. 1.28
D. 1.28
E. 1.65
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Question 186745This question is from textbook Statistical Techniques in Business and Economics
: A survey of undergraduate students in the school of Businees at Northern University revealed the following regarding the gender and majors of the students:
Major
Gender Accounting Management Finance Total
Male 100 150 50 300
Female 100 50 50 200
Total 200 200 100 500
What is the probaility of selecting a female student?
What is the probability of selcting a finance or accounting major?
What is the probability of selecting a female or an accounting major? Which rule of addition did u apply?
Are gender and major independent? Why?
What is the probability of selecting an accounting major, given that the person selected is a male?
Suppose two students are selected randomly to attend a lunch with the president of the University. What is the probability that both of these selected are accounting majors?This question is from textbook Statistical Techniques in Business and Economics
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Question 187100: A study of the amount of time it takes a mechanic to rebuild the transmission of a 1992 Chevrolet Cavalier shows that the mean is 8.4 hours and the standard deviation is 2.4 hours. If 36 mechanics are randomly selected, find the probability that their mean rebuild time is more than 8.8 hours.
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Question 187072: Describe the action that would result in a type I error and a type II error if each of the following null hypotheses were tested.
a. H0: There is no waste in US Defense Department spending
b. H0: This fast-food menu is not low fat
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Question 187070: Determine the critical region and critical values for z that would be used to test the null hypothesis at the given level of significance, as described in each of the following:
a. H0: = 25 and Ha: ≠ 25, α = 0.10
b. H0: ≤ 32 and Ha: >32, α = 0.01
c. H0: ≥13 and Ha: <13, α = 0.05
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Question 187065: By measuring the amount of time it takes a component of a product to move from one workstation to the next, an engineer has estimate that the standard deviation is 4.5 seconds.
a. How many measurements should be made in order to be 95% certain that the maximum error of estimation will not exceed 1 second?
b. What sample size is required for a maximum error of 2 seconds?
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Question 187060: 1. There are 4 contestants in a bicycle race. In how many different orders can they cross the finish line?
a. 4 b. 10 c. 24 d. 16
2. Clayton has to read 3 books for English Class. He can choose from a list of 5 books. HOw many different combinations of 3 books are possible?
a. 30 b. 15 c. 10
3.Carly is making cupcakes with nuts.She can choose between 4 flavors of cupcakes,3 colors of frosting,& 2 kinds of nuts. She chooses one flavor, one color & one kind of nut. How many different cupcakes could be made? a.10 b.16 c.4 d.24
4.In a bag of candies there are 13 red candies,13 green candies,13 yellow candies,& 13 blue candies.If you choose 1 candy from the bag,what is the probability the candy will not be blue? a.3/4 b.2/3 c.1/4 d.1/2
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Question 187217: In testing the hypothesis, H0: ≥ 28.7 and Ha: < 28.7, using the p-value approach, a p-value of 0.0764 was obtained. If α = 9.8, find the sample mean which produced this p-value given that the sample of size n = 40 was randomly selected
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