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Tutors Answer Your Questions about Probability-and-statistics (FREE)
Question 136143: Need help
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 2.4 inches. Jennifer is taller than 90% 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.
Inches =
Click here to see answer by vleith(1977)   |
Question 136080: Can someone help me with these 2 problems. My instructor asked this question and I have no clue as to what is going on here. Thanks In Advance.
1. Imagine this scenario at your marketing department ..
You have been given the task of showing that there is a difference between gender and potato chip preferences.
A colleague has obtained some sample data for you:
Lays Jays Better Maid Private Label
Male 16 6 5 10
Female 7 4 11 7
>> how will you proceed ??
2. 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 the 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 a= .05? (a) State the hypothesis for a right -tailed test. (b) Obtain a test statistic and p-value assuming equal variances. Interprest 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 a-.05, showing all steps clearly
Click here to see answer by stanbon(26259) |
Question 136232: Instructor Dorff wants to test the hypothesis that students who finish an exam earlier .... get a better score.
She kept track of the order of the submission of a recent test;
>> the first 25 papers showed a mean score of 77.1 with std deviation of 19.6
>> the second 24 papers showed a mean score of 69.3 with std deviation of 24.9
>> state the hypothesis for a right tailed test and test at the 0.05 level of significance .. and determine if the difference in scores is significant
Click here to see answer by stanbon(26259) |
Question 136270: 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
construct a 90 percent confidence interval for the true mean weight.
what sample size would be necessary to estimate the true weight with an error of + 0.03 grams with 90 percent confidence?
Click here to see answer by stanbon(26259) |
Question 136327: A college baseball coach read in a sports magazine that the average fastball speed of all the pitchers who competed last year in the college world series was 90.4 mph. The 16 pitchers who tried out for the school’s team this year averaged 88.2 mph, and the standard deviation was 3.4 mph. What is the value of the test statistic?
a. –25.9
b. –0.65
c. –2.59
d. 0.65
Click here to see answer by stanbon(26259) |
Question 136326: The e-mail usage for two different plants of a large company was compared at level of significance 0.05. Samples of ten employees were selected at each plant. The mean number of e-mail messages sent per employee for one plant was 15.5 per week and the standard deviation was 5.0. For the other plant, the mean was 18.4 and the standard deviation was 1.6. For the test of equal population means (assuming equal population variances), the degrees of freedom, the absolute value of the computed test statistic, and the critical values for the test statistic respectively are:
a. 18, 1.75, ± 2.101
b. 11, 1.75, ± 2.201
c. 18, 1.75, ± 1.96
d. 11, 2.201, ± 1.75
Click here to see answer by stanbon(26259) |
Question 136317: The manufacturer of Advil, a common headache remedy, recently developed a new formulation of the drug that is claimed to be more effective. To evaluate the new drug a sample of 500 current users is asked to try it. After a one month trial, 400 indicated the new drug was more effective in relieving the headache. At the same time, a sample of 350 current Advil users is given the current drug but told it is the new formulation. From this group 300 said it was an improvement. At the .01 significance level can we conclude that the new drug is more effective?
Ho
H1
Alpha:
CV:
What Formula?
Click here to see answer by stanbon(26259) |
Question 136316: A Cell phone company offers two plans to its subscribers. At the time new subscribers sign up they are asked to provide some demographic information. The mean yearly income for a sample of 42 subscribers to plan A is $57,000 with a standard Deviation of $6,000. For a sample of 50 subscribers to plan B the mean income is $63,000 with a standard deviation of $4,900. At a significance of 0.05 is there a difference in between the two plans?
Ho
H1
Alpha:
CV:
What Formula?
Click here to see answer by stanbon(26259) |
Question 136335: Assume the likelihood that any flight on Northwest Airlines arrives within 15 minutes of the scheduled time is 0.90. We select four flights from yesterday for study. (Question 50)
a. What is the likelihood all four of the selected flights arrived within 15 minutes of scheduled time?
b. What is the likelihood at least one of the selected flights did not arrive within 15 minutes of the scheduled time?
c. What is the likelihood that none of the selected flights arrived within 15 minutes of the scheduled time?
Click here to see answer by stanbon(26259) |
Question 136358: A nationwide test taken by high school sophomores and juniors has three sections, each scored on a scale of 20 to 80. In a recent year, the national mean score for the writing section was 51.2. Based on this information, complete the folloiwng staements about the distribution of the scores on the writing section for the recent year.
1. According to Chebyshev's theorem, at least ____% fo the scores lie within 2.5 standard deviations of the mean, 51.2.
2. Suppose that the distribution is bell shaped. If approximately 99.7% of the scores lie between 23.6 and 78.8, then the approximate value of the standard deviation for the distribution, according to the empirical rule, is _____?
Click here to see answer by Edwin McCravy(2920) |
Question 136384: A student team examined parked cars in four different suburban shopping malls. One hundred vehicles were examined in each location. Research question: At α = .05, does vehicle type vary by mall location? (Data are from a project by MBA students Steve Bennett, Alicia Morais, Steve Olson, and Greg Corda.)
Vehicle Type Somerset Oakland Great Lakes Jamestown Row Total
Car 44 49 36 64 193
Minivan 21 15 18 13 67
Full-sized Van 2 3 3 2 10
SUV 19 27 26 12 84
Truck 14 6 17 9 46
Col Total 100 100 100 100 400
Click here to see answer by stanbon(26259) |
Question 136383: Sixty-four students in an introductory college economics class were asked how many credits they had earned in college, and how certain they were about their choice of major. Research question: At α = .01, is the degree of certainty independent of credits earned?
Credits Earned Very Uncertain Somewhat Certain Very Certain Row Total
0–9 12 8 3 23
10–59 8 4 10 22
60 or more 1 7 11 19
Col Total 21 19 24 64
Click here to see answer by stanbon(26259) |
Question 136388: Sixty-four students in an introductory college economics class were asked how many credits they
had earned in college, and how certain they were about their choice of major. Research question:
At α = .01, is the degree of certainty independent of credits earned?
Credits Earned very Uncertain Somewhat Certain Very Certain Row Total
0–9 12 8 3 23
10–59 8 4 10 22
60 or more 1 7 11 19
Col Total 21 19 24 64
Click here to see answer by stanbon(26259) |
Question 136397: A cab company computed its mean fare from O'Hare Airport to a hotel to be $25.35 Based on this information, complete the following statements about the distribution of the cab fare to the hotel.
a. According to Chebyshev's theorem, at least ______% of the fare lies within 1.5 standard deviations of the mean, 25.35 dollars.
b. Suppose that the distribution is bell shaped. If aproximately 99.7% of the fares lie between 14.67 dollars and 36.03 dollars, then the approximate value of the standard deviation for the distribution, according to the empirical rule is ___________
Click here to see answer by stanbon(26259) |
Question 136403: A college has 64 students. 36 are sophomores, 39 mathematic majors and 6 are neither. A student is picked at random from the class.
a. What is the probability that the student is both a sophomore and a math major?
b. If the student is a sophomore, what is the probability that he is also a math major? Write yor response as fractions. Thank you.
Click here to see answer by stanbon(26259) |
Question 136415: Hypothesis test for the difference of population means: t test
An industrial plant wants to determine which of two types of fuel, electric or gas, is more cost efficient (measured in cost per unit of energy). Independent random samples were taken of plants using electricity and plants using gas. These samples consisted of plants using electricity, which had a mean cost per unit of and standard deviation of , and plants using gas, which had a mean of and standard deviation of . Assume that the populations of costs per unit are normally distributed for each type of fuel, and assume that the variances of these populations are equal. Can we conclude, at the level of significance, that the mean cost per unit for plants using electricity, , is greater than the mean cost per unit for plants using gas, ?
Perform a one tailed test. Carry your intermediate answers to at least three decimal places.
Null hypothesis—Ho:
Alternate Hypothesis—H1:
The type of test statistic:
The value of the test statistic (round to three decimal places)
The p-value (round to three decimal places:
Can we conclude that the mean cost per unit for plants using electricity is greater than the mean cost per unit for plants using gas? Yes or no.
Click here to see answer by stanbon(26259) |
Question 136381: 15.28 Can people really identify their favorite brand of cola? Volunteers tasted Coca-Cola Classic,Pepsi, Diet Coke, and Diet Pepsi, with the results shown below. Research question: At α = .05, is the correctness of the prediction different for the two types of cola drinkers? Could you identify your favorite brand in this kind of test? Since it is a 2 × 2 table, try also a two-tailed two-sample z test for π1 = π2 (see Chapter 10) and verify that z2 is the same as your chi-square statistic.Which test do you prefer? Why? (Data are from Consumer Reports 56, no. 8 [August 1991], p. 519.)
Click here to see answer by stanbon(26259) |
Question 136428: A newspaper article reported that people spend a mean of 6.5 hours per day watching TV, with a standard deviation of 1.7 hours. A psychologist would like to conduct interviews with the 15% of the population who spend the most time watching TV. She assumes that the daily time people spend watching TV is normally distributed. At least how many hours of daily TV watching is necessary for a person to be eligible for the interview. Carry your intermediate comutations to a least four decimal places. Round your answer to at least one decimal place.
Thank you.
Click here to see answer by stanbon(26259) |
Question 136373: 26. A study regarding the relationship between age and the amount of pressure sales personnel
feel in relation to their jobs revealed the following sample information. At the .01 significance
level, is there a relationship between job pressure and age?
Degree of Job Pressure
Age (years) Low Medium High
Less than 25 20 18 22
25 up to 40 50 46 44
40 up to 60 58 63 59
60 and older 34 43 43
Click here to see answer by stanbon(26259) |
Question 136372: 12. For many years TV executives used the guideline that 30 percent of the audience were
watching each of the prime-time networks and 10 percent were watching cable stations on
a weekday night. A random sample of 500 viewers in the Tampa–St. Petersburg, Florida,
area last Monday night showed that 165 homes were tuned in to the ABC affiliate, 140 to
the CBS affiliate, 125 to the NBC affiliate, and the remainder were viewing a cable station.
At the .05 significance level, can we conclude that the guideline is still reasonable?
Click here to see answer by stanbon(26259) |
Question 136449: Need help on this problem.....
standard normal probabilities
Let Z be a standard normal random variable. Calculate the following probabilities using the calculator provided. Round your responses to at least three decimal places.
P (Z > -1.53) =
P (-0.90 < Z < 2.12) =
Click here to see answer by stanbon(26259) |
Question 136446: The American Sugar Producers Association wants to estimate the mean yearly sugar consumption. A sample of 16 people reveals the mean yearly consumption to be 60 pounds with a standard deviation of 20 pounds.
a. What is the value of the population mean? What is the best estimate of this value?
b. Explain why we need to use the t distribution. What assumption do you need to make?
c. For a 90% confidence interval, what is the value of t?
d. Develop the 90% confidence interval for the population mean.
e. Would it be reasonable to conclude that the population mean is 63 pounds?
Click here to see answer by stanbon(26259) |
Question 136371: 30. There are four auto body shops in a community and all claim to promptly serve customers.
To check if there is any difference in service, customers are randomly selected from each
repair shop and their waiting times in days are recorded. The output from a statistical software
package is:
Summary
Groups Count Sum Average Variance
Body Shop A 3 15.4 5.133333 0.323333
Body Shop B 4 32 8 1.433333
Body Shop C 5 25.2 5.04 0.748
Body Shop D 4 25.9 6.475 0.595833
ANOVA
Source of Variation SS df MS F p-value
Between Groups 23.37321 3 7.791069 9.612506 0.001632
Within Groups 9.726167 12 0.810514
Total 33.09938 15
Is there evidence to suggest a difference in the mean waiting times at the four body shops?
Use the .05 significance level.
Please help
Click here to see answer by stanbon(26259) |
Question 136467: A real estate developer is considering investing in a shopping mall on the outskirts of Dallas, Texas. Various parcels of land are being evaluated. Of particular importance is the income in the area surrounding the proposed mall. A random sample of families is selected near each proposed mall. Following are the sample results. At the 0.05 significance level, can the developer conclude there is a difference in the mean income? Use the usual 5 step hypothesis testing procedure.
McKinney Richardson Allen Plano
4 2 1 2
8 3 2 3
4 4 3 1
3
a) State the null and alternate hypothesis
b) What is alpha?
c) What is n?
d) What is K?
e) Formulas:
a) SS total=
b) SSE=
c) SST=
d) dfn=
e) dfd=
f) MST=
g) MSE=
h) F=
Thanks in Advance! :-) Also, the numbers in the cities column are listed individualy and vertically. For some reason they get bunched up on the system.
Click here to see answer by stanbon(26259) |
Question 136368: 8.64 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 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?
Click here to see answer by stanbon(26259) |
Question 136486: When a confidence interval for a population mean is constructed from sample data,
A) we can conclude that the population mean is in the interval
B) we can conclude that the population mean is not in the interval
C) we can conclude, with a stated level of confidence, that the population mean is in the interval
D) we cannot make any inferences.
Click here to see answer by stanbon(26259) |
Question 136488: 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.
Click here to see answer by stanbon(26259) |
Question 136507: I am having problems trying to figure out can you help thanks.
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.
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
Click here to see answer by stanbon(26259) |
Question 136507: I am having problems trying to figure out can you help thanks.
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.
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
Click here to see answer by Edwin McCravy(2920) |
Question 136511: Please help, no text book.
Consider this problem:
Instructor Dorff wants to test the hypothesis that students who finish an exam earlier .... get a better score.
She kept track of the order of the submission of a recent test;
>> the first 25 papers showed a mean score of 77.1 with std deviation of 19.6
>> the second 24 papers showed a mean score of 69.3 with std deviation of 24.9
>> state the hypothesis for a right tailed test and test at the 0.05 level of significance .. and determine if the difference in scores is significant
Click here to see answer by stanbon(26259) |
Question 136541: The lifetime of a certain brand of battery is known to have a standard deviation of 23 hours. Suppose that a random sample of 70 such batteries has a mean lifetime of 35.1 hours. Based on this sample, find a 95% confidence interval for the true mean lifetime of all batteries of this brand.
Click here to see answer by stanbon(26259) |
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