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Tutors Answer Your Questions about Probability-and-statistics (FREE)
Question 183325: A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech Pages Plus Yello Pages. On each page, the mean area devoted to display ads was measured (a display ad is large block of multicolored illustrations, maps, and text). The data (in sguare 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% 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% confidence? (d) If this is not a reasonable requirement, suggest one that is.
Construct
Click here to see answer by stanbon(26259)   |
Question 183491: 12.50 In the following regression, X = total assets ($ billions), Y = total revenue ($ billions), and n = 64 large banks. (a) Write the fitted regression equation. (b) State the degrees of freedom for a two tailed test for zero slope, and use Appendix D to find the critical value at α = .05. (c) What is your conclusion about the slope? (d) Interpret the 95 percent confidence limits for the slope. (e) Verify that F = t2 for the slope. (f) In your own words, describe the fit of this regression.
R2 0.519
Std. Error 6.977
n 64
ANOVA table
Source SS df MS F p-value
Regression 3,260.0981 1 3,260.0981 66.97 1.90E-11
Residual 3,018.3339 62 48.6828
Total 6,278.4320 63
Regression output confidence interval
Variables coefficients std. error t (df = 62) p-value 95% lower 95% upper
Intercept 6.5763 1.9254 3.416 .0011 2.7275 10.4252
X1 0.0452 0.0055 8.183 1.90E-11 0.0342 0.0563
Click here to see answer by stanbon(26259) |
Question 183502: 2. The score on the entrance test for a well known law school has a mean score of 200 points and a standard deviation of 50 points. At value should the lowest passing score be set if the school wishes only 2.5% of those taking the entrance test to pass?
Click here to see answer by stanbon(26259) |
Question 183501: 1. In an article in the Journal of Management, Morris, Avila and Allen studied innovation by surveying firms to find the number of new products introduced by the firms. A random sample of 100 California based firms are selected. Each firm is asked to report the number of new products introduced last year. The survey found that on average these firms introduced 5.68 products with a standard deviation of 8.70. Compute a 98% confidence interval for the new products introduced last year.
Click here to see answer by stanbon(26259) |
Question 183472: In a clinical trial, a drug used to reduce fever caused side effects in 2% of patients who took it. Three patients were selected at random. Find the probability that none of those patients had side effects.
Click here to see answer by stanbon(26259) |
Question 183329: Biting an unpopped kernel of popcorn hurts! 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% confidence intervel 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?
Click here to see answer by stanbon(26259) |
Question 183782: Hi.
I am pretty sure I know how to do this, but I just want to double check because I am still confused.
Tommy is playing a carnival game. Ten $5 bills, ten $10 bills, and ten $20 bills are in a box. while blindfolded, Tommy must take out one bill at a time from the box. The game ends when Tommy removes three of the same type of bills. What is the greatest amount of money Tommy can win if he wins all the money he draws?
Help!
Click here to see answer by josmiceli(3003) |
Question 183782: Hi.
I am pretty sure I know how to do this, but I just want to double check because I am still confused.
Tommy is playing a carnival game. Ten $5 bills, ten $10 bills, and ten $20 bills are in a box. while blindfolded, Tommy must take out one bill at a time from the box. The game ends when Tommy removes three of the same type of bills. What is the greatest amount of money Tommy can win if he wins all the money he draws?
Help!
Click here to see answer by jim_thompson5910(13787) |
Question 183829: The yankees are playing the red sox and alex rodregous(for the Yankees) hit a 3 run home run and they win by 3. Togethr there scores equal 31. What is the score of each team? Can you solve this in 3 ways using a system please.
Click here to see answer by halbren(10) |
Question 183819: I hopr some one can help me, I am having some troulbe with my statistics homework.I have two questions.
Find the indicated binomial probabilities. Round to the nearest 3 decimal places.
Hot Shot Battery manufactures batteries in batches of 15 with a defective rate of 10% (1 points each)
a.What is the probability that exactly 2 will be defective?
b.What is the probability that between 2 and 4 inclusive will be defective?
c. What is the probability that no batteries will be defective? d. Find the mean
e. Find the variance 2
A Multiple-choice test has 15 questions with each having 4 possible answers with one correct. Assume a student answers every question.
(2.5 points each)
a. What is the probability of getting exactly 5 correct answers?
b. What is the probability of getting less than 6 correct answers?
I would like to thank you in advance for your help, and using your own to help me out.
Click here to see answer by stanbon(26259) |
Question 183891: 1. A poll of 400 people from Dobbs Ferry showed 250 preferred chocolate raspberry coffees while 170 out of 350 in Irvington preferred the same flavor. To test the hypothesis that there is no difference in preferences in the two villages, what is the alternate hypothesis?
A)
B)
C)
D)
Click here to see answer by tvandenberg(45) |
Question 183916: Model one accounts for 80% of unit sales and model two for 20% of unit sales. However, they have to replace 10% of model one and 18% of model two because of defects.If a unit is selected at random what is the probability that it is defective?
Click here to see answer by edjones(3292)  |
Question 183892: 3. When is it appropriate to use the paired difference t-test?
A) Four samples are compared at once
B) Any two samples are compared
C) Two independent samples are compared
D) Two dependent samples are compared
Click here to see answer by stanbon(26259) |
Question 183893: Using two independent samples, two population means are compared to determine if a difference exists. The number in the first sample is fifteen and the number in the second sample is twelve. How many degrees of freedom are associated with the critical value?
A) 24
B) 25
C) 26
D) 27
Click here to see answer by stanbon(26259) |
Question 184106: Hi can someone please assist me with this problem from Doane−Seward: Applied
Statistics in Business and Economics, ch. 12:
For each sample, do a test for zero correlation. (a) Use Appendix D to find the critical value of tα. (b) State the hypotheses about ρ. (c) Perform the t test and report your decision. (d) Find the critical value of rα and use it to perform the same hypothesis test.
a. r = +.45, n = 20, α = .05, two-tailed test
b. r = −.35, n = 30, α = .10, two-tailed test
c. r = +.60, n = 7, α = .05, one-tailed test
d. r = −.30, n = 61, α = .01, one-tailed test
Thank you
Click here to see answer by stanbon(26259) |
Question 184157: (a) Plot the data on U.S. general aviation shipments. (b) Describe the pattern and discuss possible causes. (c) Would a fitted trend be helpful? Explain. (d) Make a similar graph for 19922003 only. Would a fitted trend be helpful in making a prediction for 2004? (e) Fit a trend model of your choice to the 19922003 data. (f) Make a forecast for 2004, using either the fitted trend model or a judgment forecast. Why is it best to ignore earlier years in this data set? Airplanes
U.S. Manufactured General Aviation Shipments, 19662003
Year Planes Year Planes Year Planes Year Planes
1966 15,587 1976 15,451 1986 1,495 1996 1,053
1967 13,484 1977 16,904 1987 1,085 1997 1,482
1968 13,556 1978 17,811 1988 1,143 1998 2,115
1969 12,407 1979 17,048 1989 1,535 1999 2,421
1970 7,277 1980 11,877 1990 1,134 2000 2,714
1971 7,346 1981 9,457 1991 1,021 2001 2,538
1972 9,774 1982 4,266 1992 856 2002 2,169
1973 13,646 1983 2,691 1993 870 2003 2,090
1974 14,166 1984 2,431 1994 881
1975 14,056 1985 2,029 1995 1,028
Click here to see answer by stanbon(26259) |
Question 183351: According to the boss of the retail outlets, these are the figures of the daily sales for the month of November and December. The boss claims that the average daily sales exceed $250 000.
November 08 (in $000)
215
180
240
246
267
305
245
311
265
224
285
255
235
268
290
187
263
255
266
278
233
203
226
264
335
320
December 08 (in $000)
229
185
238
267
224
280
260
265
285
210
235
200
204
223
187
265
280
240
248
268
240
215
225
245
240
255
320
Determine if the mean daily sale in December is significantly lower than November 2008 with the following:
a) State the null and alternative hypothesis and explain how it is derived.
b) Which would be an appropriate test for this case?
c) State the assumptions made in performing this test and is it reasonable?
d) Perform an appropriate hypothesis test with alpha=0.05 using critical value approach.
Click here to see answer by stanbon(26259) |
Question 184191This question is from textbook saxon algebra 2
: The table shows the results of a survey that asked students from three grade levels to pick their favorite fruit from those listed. Find P(Banana\11).
10th 11th 12th
apple 23 35 21
orange 16 12 30
pear 8 7 12
banana 32 24 18
I worked it out thus far: banana/11: 74/24=3.08 or 31%. Am I correct?This question is from textbook saxon algebra 2
Click here to see answer by stanbon(26259) |
Question 184258: Hi this is not from a book, I wanted to know if I am on the right track?:
A shoe store owner is interested in determining if the average weight of a package of shoes sold in the store weighs two pounds. An appropriate alternate hypothesis for this study is
a. H1: (Mu) = 2 lb
b. H1: (Mu) not equal to 2 lb
c. H1: (Mu) > 2 lb
d. H1: (Mu) < 2 lb
*I was thinking (d.), would that be the right answer?
If it isn't why not, and which one would be the most appropriate?
Thank you
Click here to see answer by stanbon(26259) |
Question 184261: Hi this is not from a book, can you please tell me if I am on the right track?:
An ice cream store manager thinks that the average bill paid by his customers is $10. To test his hypothesis, the next 20 tabs are tallied. All of them are over $10. Therefore, he can conclude immediately that the average bill paid by all of his customers
a. exceeds $10.
b. may be less than, equal to, or greater than $10.
c. is less than $10.
d. equals $10.
*I was thinking (a.), is this the correct answer?
If not can you please explain why, and which one would be the best answer?
Thank you
Click here to see answer by stanbon(26259) |
Question 184266: Hi,
This is not from a book, can you please tell me if I am on the right track?:
The appropriate "null hypothesis" for a lower-tail test to determine if mean body weight of all the women who have joined a health club is less than 150 pounds would be
a. H0: (Mu)greater than or equal to 150 lb.
b. H0: (Mu) < 150 lb.
c. H0: (Mu) = 150 lb.
d. H0: (Mu)not equal to 150 lb.
*I was thinking (a.), is this the correct answer?
If not can you please explain why, and which one would be the best answer?
Thank you
Click here to see answer by stanbon(26259) |
Question 184291: Combinations
A pizza parlor has a choice of toppings for its pizzas. From these toppings, how many different -topping pizzas can be ordered? Assume that the order in which the toppings are listed does not matter.
Click here to see answer by rapaljer(3620) |
Question 184293: A random sample of 10 miniature Tootsie Rolls was taken from a bag. Each piece was weighed on a very accurate scale. The results in grams were
3.087 3.131 3.241 3.241 3.270 3.353 3.400 3.411 3.437 3.477
(a) Construct a 90 percent confidence interval for the true mean weight. (b) What sample size would be necessary to estimate the true weight with an error of } 0.03 grams with 90 percent confidence?
(c) Discuss the factors which might cause variation in the weight of Tootsie Rolls during
manufacture.
Click here to see answer by stanbon(26259) |
Question 184292: In 1992, the FAA conducted 86,991 pre-employment drug tests on job applicants who were to be engaged in safety and security-related jobs, and found that 1,143 were positive. (a) Construct a 95 percent confidence interval for the population proportion of positive drug tests. (b) Why is the normality assumption not a problem, despite the very small value of p? (Data are from Flying 120,no. 11 [November 1993], p. 31.)
Click here to see answer by stanbon(26259) |
Question 184377: Hi,
Can you please tell me if I am on the right track?
A linear regression between Y and X produced the following equation for the least squares line:
= 3.16 4.3x
Which of the following statements concerning this relationship is true?
a. For every one-unit increase in X, Y increases 4.3 units.
b. For every one-unit increase in Y, X decreases 4.3 units.
c. For every one-unit increase in X, Y decreases 4.3 units.
d. For every one-unit increase in Y, X increases 4.3 units.
I was thinking (c.), is this the correct answer?
If not can you please explain why, and which one would be the best answer?
Thank you
Click here to see answer by solver91311(5072)  |
Question 184365: 13. For the following scores, find the (a) mean, (b) median, (c) sum of squared deviations, (d) variance, and (e) standard deviation:
3.0, 3.4, 2.6, 3.3, 3.5, 3.2
THANKS THANKS
Click here to see answer by stanbon(26259) |
Question 184431: Payne (2001) gave participants a computerized task in which they first see a face and then a picture of either a gun or a tool. The task was to press one button if it was a tool and a different one if it was a gun. Unknown to the participants while they were doing the study, the faces served as a prime (something that starts you thinking a particular way) and half the time were of a black person and half the time of a white person. Table 2-8 shows the means and standard deviations for reaction times (time to decide if the picture is of a gun or a tool) after either a black or white prime. (In Experiment 2, participants were told to decide as fast as possible.) Explain the results to a person who has never had a course in statistics. (Be sure to explain some specific numbers as well as the general principle of the mean and standard deviation.)
Click here to see answer by stanbon(26259) |
Question 184458: Suppose you want to conduct a survey of the attitude of psychology graduate students studying clinical psychology towards psychoanalytic methods of psychotherapy. One approach would be to contact every psychology graduate student you know and ask them to fill out a questionnaire about it. (a) What kind of sampling method is this? (b) What is a major limitation of this kind of approach?
Click here to see answer by stanbon(26259) |
Question 184492: A letter is taken at random from the letters of the word 'statistics' and another letter is taken at random from the letters of the word 'assistant'. what is the probability that they are the same letter?
Click here to see answer by Jasmine=](1) |
Question 184596: Could someone please help me solve this? Thank you.
If Punxsutawney Phil sees his shadow on the first Monday in February, then legend says that winter will last 6 more weeks. In 118 years, Phil has seen his shadow 104 times. (a) What is the probability that Phil will see his shadow on a randomly chosen Groundhog Day? (b) What kind of probability is this?
Click here to see answer by jim_thompson5910(13787) |
Question 184591: I NEED Help in statistics. Could someone please help me with this. Thank you.
The chair of the board of directors says, There is a 45% chance this company will earn a profit, a 35% chance it will break even, and a 20% chance it will lose money next quarter.
a. Find the probability they will not lose money next quarter.
b. Find the probability they will lose money next quarter.
Click here to see answer by vleith(1977) |
Question 184491: A person scores 81 on a test of verbal ability and 6.4 on a test of quantitative ability. For the verbal ability test, the mean for people in general is 50 and the standard deviation is 20. For the quantitative ability test, the mean for people in general is 0 and the standard deviation is 5. Which is this persons stronger ability: verbal or quantitative? Explain your answer to a person who has never had a course in statistics.
Click here to see answer by stanbon(26259) |
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