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Croup Chais

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Mastering Motion: Achieving Efficiency Along a Straight Line

Croup's Textbook Answer Videos

1

Croup's Quick Ask Videos

02:29
Intro Stats / AP Statistics

The number of hits to a website follows a Poisson process. Hits
occur at the rate of 4.1 per minute between 7:00
P.M. and 11:00 P.M. Given below are three scenarios for the number
of hits to the website. Compute the probability of each scenario
between 10:12 P.M. and 10:15 P.M. Interpret each result. Show
your work
(a) exactly six
(b) fewer than six
(c) at least six
02:17
Intro Stats / AP Statistics

Suppose the random variables X1 to X4 have the following means and standard deviations: μ1 = 0.64, μ2 = 3400 kN/m, μ3 = 1, and μ4 = 5.461 m. σ1 = 0.096, σ2 = 170 kN/m, σ3 = 0.2, σ4 = 1.081 m. where μ1 is the mean value for X1, σ1 is the standard deviation for X1, up to μ4 which is the mean value for X4 and σ4 which is the standard deviation for X4. Under the assumption that Rh and X1Rv have Weibull distributions, amend your Excel file created during the practical class of week 9 and from it calculate the probability that the breakwater is stable. To 2 decimal places, what is this probability (in %)?
00:47
Intro Stats / AP Statistics

Using 50 random numbers given below, compute the mean and
standard deviation. 0.940852 0.150648 0.036836 0.800648 0.743675
0.509732 0.808893 0.130527 0.197464 0.872007 0.761749 0.063958
0.471359 0.312392 0.092033 0.361882 0.486803 0.367253 0.705160
0.801682 0.310460 0.354447 0.430072 0.911759 0.397931 0.835552
0.588321 0.029109 0.751805 0.769545 0.375583 0.544129 0.972983
0.483300 0.813827 0.793408 0.130703 0.447120 0.873767 0.433202
0.353709 0.983431 0.731785 0.288059 0.055772 0.460438 0.027932
0.605089 0.744591 0.225487 Mean = (to 6 decimals) Standard
deviation = (to 6 decimals)
02:23
Intro Stats / AP Statistics

In a city of 150,000 people in mid-year of 2020, there are
69,886 males and 80,114 females. In 2020, 1250 people die (675
males and 575 females). There were 58 cases (41 males and 17
females) of lung cancer per year. Of these, 43 died (32 males and
11 females). A total of 53 new babies were born alive during the
year. There were 27 male infants and 26 female infants. One infant
died during the year. Of the newborns, 2 were low birthweight.
Calculate the following and report the units. Be sure to have at
least one number to the left of the decimal point and one to the
right. Summarize your results in one sentence.
a. What is the overall mortality rate per 100,000 for men in
2020?
b. What is the incidence per 100,000 of lung cancer in men in
2020?
c. What is mortality rate due to lung cancer in men in 2020?
d. How does the case fatality rate for lung cancer in men
compare to that in women in 2020?
e. What type of incidence (mortality) have you been using to
answer part a – c?
03:34
Intro Stats / AP Statistics

A large sample of cigarette smokers (N = 2,500) was obtained in order to see if there was a relationship between how much a person smoked and his or her physical health. To measure the amount of smoking, each person reported how many years he or she had been smoking cigarettes. The mean, Mx = 22 years, with a standard deviation of 9. As a measure of physical health, each person’s lung function was measured. This was reported as a percent of the predicted normal level, so lower scores mean worse functioning. A lung function score of 100 would mean that the person’s lung capacity was normal for their age and sex. A score of 50 would mean that the smoker’s level of lung function was only 50% of what was expected for a person of the same age and sex. The mean level of function (My) was 76%, with a standard deviation of 13. The average person had been smoking for 22 years and had lungs functioning at 76% of what was expected. Not surprisingly, the relationship between years of smoking and the degree of lung function was negative and strong: r(2, 498) = -0.68, p < 0.05. As years of smoking went up, the percent of normal lung function went down.

a. Calculate the slope for the regression line.
c. Calculate the y-intercept for the regression line. (2 pts)
d. Write the regression equation using the numbers you calculated. (2 pts)
e. Use the regression equation to predict a smoker’s lung function if they have been smoking for eight years. (2 pts)
03:38
Intro Stats / AP Statistics

Fast food companies wanted to determine the average number of
times per 6-week period that people eat out at fast food
restaurants. A recent random sample of 27 people showed that the
average number of times they eat out during this interval is 29
times with a standard deviation of 7 times. a) What is the best
estimate of the value of the population mean? b) We will use the t
distribution for this question, but is there another way? If any,
what assumptions must we make? No, there is no other way in this
instance, but we have to assume the population is normal. No, there
is no other way in this instance, and we don't have to make any
assumptions. Yes, there is another way. We could choose to use the
z distribution because of the results of the central limit
theorem.
c) For a 99 percent confidence interval, what is the value of t?
For full marks, your answers should be accurate to three decimal
places.
d) Develop the 99 percent confidence interval for the population
mean. For full marks, your answers should be accurate to three
decimal places. e) Would it be reasonable to conclude that the
population mean is 34? Yes, it is reasonable. No, it is not
reasonable. We do not have enough information to decide.
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