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Moore et al-Intro to the Practice of Statistics 7e (Homework)

James Finch

Statistics, section 2, Fall 2019

Instructor: Dr. Friendly

Current Score : 0 / 27

Due : Sunday, January 27, 2030 23:30 EST

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    Here are some textbook questions from Introduction to the Practice of Statistics 7/e by David S. Moore, George P. McCabe, and Bruce A. Craig published by W. H. Freeman. Click here for a list of all of the questions coded in WebAssign. This demo assignment allows many submissions and allows you to try another version of the same question for practice wherever the problem has randomized values.

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1. –/6 points MIntroStat7 1.E.082. My Notes
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Many standard statistical methods that you will study in Part II of this book are intended for use with distributions that are symmetric and have no outliers. These methods start with the mean and standard deviation, x and s. For example, standard methods would typically be used for the IQ and GPA data here data417.dat.
(a) Find x and s for the IQ data. (Round your answers to two decimal places.)
x =
s =

(b) Find the median IQ score. It is, as we expect, close to the mean.


(c) Find the mean and median for the GPA data. The two measures of center differ a bit. (Round your answers to two decimal places.)
mean =
median =

What feature of the data (make a stemplot or histogram to see) explains the difference?

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2. –/4 points MIntroStat7 1.E.122. My Notes
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The length of human pregnancies from conception to birth varies according to a distribution that is approximately normal with mean 267 days and standard deviation 16 days. Use the 68-95-99.7 rule to answer the following questions.
(a) Between what values do the lengths of the middle 95% of all pregnancies fall?
and days

(b)How short are the shortest 2.5% of all pregnancies?
days

How long do the longest 2.5% of pregnancies last?
days
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3. –/2 points MIntroStat7 3.E.071. My Notes
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At a party there are 15 students over age 21 and 10 students under age 21. You choose at random 3 of those over 21 and separately choose at random 2 of those under 21 to interview about attitudes toward alcohol. You have given every student at the party the same chance to be interviewed: what is that chance?
%

Why is your sample not an SRS?
    
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4. –/2 points MIntroStat7 4.E.029. My Notes
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Choose a young adult (age 25 to 34 years) at random. The probability is 0.14 that the person chosen did not complete high school, 0.28 that the person has a high school diploma but no further education, and 0.24 that the person has at least a bachelor's degree.
(a) What must be the probability that a randomly chosen young adult has some education beyond high school but does not have a bachelor's degree?


(b) What is the probability that a randomly chosen young adult has at least a high school education?
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5. –/6 points MIntroStat7 4.E.030. My Notes
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There are many ways to produce crooked dice. To load a die so that 6 comes up too often and 1 (which is opposite 6) comes up too seldom, add a bit of lead to the filling of the spot on the 1 face. Because the spot is solid plastic, this works even with transparent dice. If a die is loaded so that 6 comes up with probability 0.2 and the probabilities of the 2, 3, 4, and 5 faces are not affected, what is the assignment of probabilities to the six faces? (Round your answers to three decimal places.)
P(1) =
P(2) =
P(3) =
P(4) =
P(5) =
P(6) =
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6. –/1 points MIntroStat7 5.E.024. My Notes
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The number of flaws per square yard in a type of carpet material varies with mean 1.2 flaws per square yard and standard deviation 1.1 flaws per square yard. This population distribution cannot be normal, because a count takes only whole-number values. An inspector studies 171 square yards of the material, records the number of flaws found in each square yard, and calculates x, the mean number of flaws per square yard inspected. Use the central limit theorem to find the approximate probability that the mean number of flaws exceeds 1.3 per square yard. (Round your answer to four decimal places.)
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7. 0/6 points  |  Previous Answers MIntroStat7 5.E.047. My Notes
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Typographic errors in a text are either nonword errors (as when "the" is typed as "teh") or word errors that result in a real but incorrect word. Spellchecking software will catch nonword errors but not word errors. Suppose human proofreaders catch 75% of nonword errors. You ask a fellow student to proofread an essay in which you have deliberately made 11 nonword errors.
(a) What is the mean number of errors caught? What is the mean number of errors missed? You see that these two means must add to 11, the total number of errors.
μcaught
 		=
μmissed
 		=

(b) What is the standard deviation σ of the number of errors caught? (Round your answer to four decimal places.)


(c) Suppose that a proofreader catches 90% of nonword errors, so that p = 0.9. What is σ in this case? What is σ if p = 0.99? (Round your answers to four decimal places.)
σ0.9 =
σ0.99 =

(d) What happens to the standard deviation of a binomial distribution as the probability of a success gets close to 1?
     Incorrect: Your answer is incorrect.
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