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Tutors Answer Your Questions about Probability-and-statistics (FREE)
Question 141211:
Trend lines for yearly data
A clothing manufacturer uses a trend line of the form to generate yearly forecasts of its total sales (in millions of dollars). The trend line was developed using a data set that starts in (i.e., time period corresponds to ).
Generate a forecast for total yearly sales during .
Click here to see answer by stanbon(26259)   |
Question 141200: Suppose that the heights of adult women in the United States are normally distributed with a mean of 63.5 inches and a standard deviation of 2.2inches. Jennifer is taller than 70% of the population of U.S. women. How tall (in inches) is Jennifer? Carry your intermediate computations to at least four decimal places. Round your answer to at least one decimal place.
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Question 139352: How does correlation analysis differ from regression analysis?b) What does a correlation coefficient reveal? c) State the quick rule for a significant correlation and explain its limitations. d) What sums are needed to calculate a correlation coefficient? e) What are the two ways of testing a correlation coefficient for significance?
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Question 139132: Need help please.
a. What is the F critical value to be used at the 0.05 level of significance with 7 numerator degrees of freedom and 12 denominator degrees of freedom?
b. What is the chi-square critical value with 12 degrees of freedom for a 0.05 probability?
c. What is the exact probability of a value that fits a chi-square distribution with 17 degrees of freedom being higher than 30.995?
d. I have a sample of 13 units and I want to run a hypothesis test comparing the average to a set value. The hypothesis test uses an alpha of 0.05. What critical value would be used to compare the test statistic against?
Click here to see answer by stanbon(26259) |
Question 141262: Please run a chi-square test on the price of beer per bottle and the price of beer type and state the hypothesis. Please.
Price ($)
6.24
4.79
5.96
4.7
4.11
3.85
2.52
5.46
6
3.71
6.7
4.99
4.1
5.96
6.31
6.42
7.79
5.05
5.26
5.84
7.22
6.12
7.37
6.47
6.72
7.59
6.36
6.52
6.34
7.1
4.78
4.63
5.41
6.39
5.52
6.38
5.68
5.82
5.83
7.8
2.82
3.2
3.83
4.02
3.88
4.79
4
3.95
3.27
4.02
3.26
3.19
2.9
2.36
3.93
4.25
4.03
4.02
2.86
4.03
4.02
6.49
3.24
3.6
2.99
2.75
3.9
5.42
5.63
Type of beer
1
1
1
1
1
1
1
1
1
1
1
1
1
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2
2
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2
2
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3
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4
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5
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5
5
5
5
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5
5
5
5
5
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Question 141446: 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
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Question 141513: 1. The following information is available.
H0: µ = 50
H1: µ ≠ 50
The sample mean is 49, and the sample size is 36. The population standard deviation is 5. Use a 0.05 significance level.
Answer the questions:
(a) Is this a one- or two-tailed test?
(b) What is the decision rule?
(c) What is the value of the test statistic?
(d) What is your conclusion (in plain English) regarding H0?
Click here to see answer by Edwin McCravy(2920) |
Question 141677This question is from textbook CPM Algrebra 2
: I do not understand how to make the tree diagram for this problem. I understand , or at least I think I understand, that the definates are the three coins, and the choices are heads or tails, but I keep ending up with the wrong tree. Please show me how to make the tree.This question is from textbook CPM Algrebra 2
Click here to see answer by stanbon(26259) |
Question 141632: 13.30 A researcher used stepwise regression to create regression models to predict BirthRate (births per 1,000) using five predictors: LifeExp (life expectancy in years), InfMort (infant mortality rate), Density (population density per square kilometer), GDPCap (Gross Domestic Product per capita), and Literate (literacy percent). Interpret these results. BirthRates2
Regression Analysis—Stepwise Selection (best model of each size)
153 observations
BirthRate is the dependent variable
p-values for the coefficients
Nvar LifeExp InfMort Density GDPCap Literate s Adj R2 R2
1 .0000 6.318 .722 .724
2 .0000 .0000 5.334 .802 .805
3 .0000 .0242 .0000 5.261 .807 .811
4 .5764 .0000 .0311 .0000 5.273 .806 .812
5 .5937 .0000 .6289 .0440 .0000 5.287 .805 .812
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Question 141592: A coin was flipped 60 times and came up heads 38 times. (a) At the .10 level of significance, is the coin biased towards heads? Show your decision rule and calculations. (b) Calculate a p-value and interpret it?
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Question 141594: An auditor reviewed 25 oral surgery insurance claims from a particular surgical office, determining that the mean out-of-pocket patient biling 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 hypothesis and decision rule. (b) Is this a close decision?
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Question 141514: The management of White Industries is considering a new method of assembling its golf cart. The present method requires 42.3 minutes, on the average, to assemble a cart. The mean assembly time for a random sample of 24 carts, using the new method, was 40.6 minutes, and the standard deviation of the sample was 2.7 minutes. Using a 0.10 level of significance, setup a Hypothesis test. Can we conclude that the assembly time using the new method is faster?
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Question 141448: The probability is 1 in 4,000,000 that a single auto trip in the United States will result in a fatality. Over a lifetime, an average U.S. driver takes 50,000 trips. (a) What is the probability of a fatal accident over a lifetime? Explain your reasoning carefully. Hint: Assume independent events. Why might the assumption of independence be violated? (b) Why might a driver be tempted not to use a seat belt “just on this trip”?
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Question 141846: Does lovastatin (a cholesterol-lowering drug) reduce the risk of heart attack? In a Texas study,
researchers gave lovastatin to 2,325 people and an inactive substitute to 2,081 people (average age
58). After 5 years, 57 of the lovastatin group had suffered a heart attack, compared with 97 for the
inactive pill. (a) State the appropriate hypotheses. (b) Obtain a test statistic and p-value. Interpret
the results at α = .01. (c) Is normality assured? (d) Is the difference large enough to be important?
(e) What else would medical researchers need to know before prescribing this drug widely? (Data
are from Science News 153 [May 30, 1998], p. 343.)
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Question 141845: An experimental medication is administered to 16 people who suffer from migraines. After an
hour, 10 say they feel better. Is the medication effective (i.e., is the percent who feel better greater
than 50 percent)? Use α = .10, explain fully, and show all steps.
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Question 141844: 9.65 A consumer agency tested 290 hams, finding that 64 were underweight. (a) Construct a 95 percent
confidence interval for the true percent of underweight hams. (b) If the goal is to reduce the incidence
of underweight hams to 25 percent or less, does this sample show that the goal is being
achieved? (c) Explain how this confidence interval is equivalent to a two-tailed test at α = .05.
(Data are from Detroit Free Press, March 9, 1999, p. 2A.)
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Question 141843: 9.63 In the Big Ten (the NCAA sports league) a sample showed that only 267 out of 584 freshmen football
players graduated within 6 years. (a) At α = .05 does this sample contradict the claim that at
least half graduate within 6 years? State your hypotheses and decision rule. (b) Calculate the
p-value and interpret it. (c) Do you think the difference is important, as opposed to significant?
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Question 141967: A sample of 25 concession stand purchases at the October 22 matinee of Bride of Chucky showed
a mean purchase of $5.29 with a standard deviation of $3.02. For the October 26 evening showing
of the same movie, for a sample of 25 purchases the mean was $5.12 with a standard deviation of
$2.14. The means appear to be very close, but not the variances. At α = .05, is there a difference
in variances? Show all steps clearly, including an illustration of the decision rule. (Data are from
a project by statistics students Kim Dyer, Amy Pease, and Lyndsey Smith.)
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Question 141966: To test the hypothesis that students who finish an exam first get better grades, Professor Hardtack
kept track of the order in which papers were handed in. The first 25 papers showed a mean score of
77.1 with a standard deviation of 19.6, while the last 24 papers handed in showed a mean score of
69.3 with a standard deviation of 24.9. Is this a significant difference at α = .05? (a) State the
hypotheses for a right-tailed test. (b) Obtain a test statistic and p-value assuming equal variances.
Interpret these results. (c) Is the difference in mean scores large enough to be important? (d) Is it reasonable
to assume equal variances? (e) Carry out a formal test for equal variances at α = .05, showing
all steps clearly.
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Question 141965: In Dallas, some fire trucks were painted yellow (instead of red) to heighten their visibility. During
a test period, the fleet of red fire trucks made 153,348 runs and had 20 accidents, while the fleet of
yellow fire trucks made 135,035 runs and had 4 accidents. At α = .01, did the yellow fire trucks
have a significantly lower accident rate? (a) State the hypotheses. (b) State the decision rule and
sketch it. (c) Find the sample proportions and z test statistic. (d) Make a decision. (e) Find the
p-value and interpret it. (f ) If statistically significant, do you think the difference is large enough to
be important? If so, to whom, and why? (g) Is the normality assumption fulfilled? Explain.
DATA
Accident Rate for Dallas Fire Trucks
Statistic Red Fire Trucks Yellow Fire Trucks
Number of accidents x1 = 20 accidents x2 = 4 accidents
Number of fire runs n1 = 153,348 runs n2 = 135,035 runs
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Question 141842: 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.
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Question 141841: On eight Friday quizzes, Bob received scores of 80, 85, 95, 92, 89, 84, 90, 92. He tells Prof.
Hardtack that he is really a 90+ performer but this sample just happened to fall below his true
performance level. (a) State an appropriate pair of hypotheses. (b) State the formula for the test
statistic and show your decision rule using the 1 percent level of significance. (c) Carry out the
test. Show your work. (d) What assumptions are required? (e) Use Excel to find the p-value and
interpret it.
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Question 142044: A fair coins is tossed 5 times.
What is the probability of obtaining exactly 3 heads?
I found a formula that looks like C(5,3)=5!/[3!(5-3)!]
My problem is, I don't know if this formula is right, or how to solve it. I believe this is supposed to tell you the number of possible outcomes???
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Question 142078: Please help this problem is giving me a headache.
What is the probability of choosing a man and is wearing a hat. There are 20 men with hats, 30 men without hats, 25 woman with hats, and 10 woman without hats.
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Question 142058: This is the socond problem I am struggling with. Any help would be appericated. thank you.
7.55 Tire pressure in a certain car is a normally distributed random variable with mean 30 psi (pounds per square inch) and standard deviation 2 psi. The manufacturer’s recommended correct inflation range is 28 psi to 32 psi. A motorist’s tire is inspected at random. (a) What is the probability that the tire’s inflation is within the recommended range? (b) What is the probability that the tire is under-inflated? *(c) The Alliance of Automotive Manufacturers has developed a microchip that will warn when a tire is 25 percent below the recommended mean, to warn of dangerously low tire pressure. How often would such an alarm be triggered? (See The Wall Street Journal, July 14, 2004.)
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Question 142057: I need help understanding this problem. I am lost
In the Ardmore Hotel, 20 percent of the customers pay by American Express credit card. (a) Of the next 10 customers, what is the probability that none pay by American Express? (b) At least two? (c) Fewer than three? (d) What is the expected number who pay by American Express? (e) Find the Standard deviation.
Any help would be great. Thank you
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Question 142256: Please help with this problem.
You are given 12 to 1 odd against hitting a solid 17 on Roulette number. This means that you win $12 if you succeed and you lose $1 if you fail. Calculate the expected value for one roll.
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Older solutions: 1..45, 46..90, 91..135, 136..180, 181..225, 226..270, 271..315, 316..360, 361..405, 406..450, 451..495, 496..540, 541..585, 586..630, 631..675, 676..720, 721..765, 766..810, 811..855, 856..900, 901..945, 946..990, 991..1035, 1036..1080, 1081..1125, 1126..1170, 1171..1215, 1216..1260, 1261..1305, 1306..1350, 1351..1395, 1396..1440, 1441..1485, 1486..1530, 1531..1575, 1576..1620, 1621..1665, 1666..1710, 1711..1755, 1756..1800, 1801..1845, 1846..1890, 1891..1935, 1936..1980, 1981..2025, 2026..2070, 2071..2115, 2116..2160, 2161..2205, 2206..2250, 2251..2295, 2296..2340, 2341..2385, 2386..2430, 2431..2475, 2476..2520, 2521..2565, 2566..2610, 2611..2655, 2656..2700, 2701..2745, 2746..2790, 2791..2835, 2836..2880, 2881..2925, 2926..2970, 2971..3015, 3016..3060, 3061..3105, 3106..3150, 3151..3195, 3196..3240, 3241..3285, 3286..3330, 3331..3375, 3376..3420, 3421..3465, 3466..3510, 3511..3555, 3556..3600, 3601..3645, 3646..3690, 3691..3735, 3736..3780, 3781..3825, 3826..3870, 3871..3915, 3916..3960, 3961..4005, 4006..4050, 4051..4095, 4096..4140, 4141..4185, 4186..4230, 4231..4275, 4276..4320, 4321..4365, 4366..4410, 4411..4455, 4456..4500, 4501..4545, 4546..4590, 4591..4635, 4636..4680, 4681..4725, 4726..4770, 4771..4815, 4816..4860
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