O Suppose that the distribution of scores in each grade Normal. Then both sets of transformed scores have the 100, 20) distribution. What percent of third-graders ve scores less than 75? What percent of sixth-graders ve scores less than 75? 177 Use software to generate some data. Most statis-

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Chapter1: Starting With Matlab
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1.176(d),1.177

A market researcher selects a large sample of potential
car buyers. For each consumer, she records gender, age,
household income, and automobile preference. Which of
these variables are categorical and which are quantitative?
1.175 Two distributions. If two distributions have
exactly the same mean and standard deviation, must
their histograms have the same shape? If they have the
same five-number summary, must their histograms have
the same shape? Explain.
1.176 Norms for reading scores. Raw scores on
behavioral tests are often transformed for easier compari-
son. A test of reading ability has mean 70 and standard
deviation 10 when given to third-graders. Sixth-graders
have mean score 80 and standard deviation 11 on the
same test. To provide separate "norms" for each grade,
we want scores in each grade to have mean 100 and stan-
dard deviation 20.
(a) What linear transformation will change third-grade
scores x into new scores new = a + bx that have the
desired mean and standard deviation? (Use b> 0 to
preserve the order of the scores.)
(b) Do the same for the sixth-grade scores.
(c) David is a third-grade student who scores 72 on
the test. Find David's transformed score. Nancy is a
sixth-grade student who scores 78. What is her transformed
score? Who scores higher within his or her grade?
(d) Suppose that the distribution of scores in each grade
is Normal. Then both sets of transformed scores have the
N(100, 20) distribution. What percent of third-graders
have scores less than 75? What percent of sixth-graders
have scores less than 75?
1.177 Use software to generate some data. Most statis-
tical software packages have routines for generating val-
ues of variables having specified distributions. Use your
statistical software to generate 30 observations from the
N(25, 8) distribution. Compute the mean and standard
deviation and s of the 30 values you obtain. How close
are x and s to the μ and o of the distribution from which
the observations were drawn? Repeat 19 more times the
process of generating 30 observations from the N(25, 8)
distribution and recording x and s. Make a stemplot of
the 20 values of and another stemplot of the 20 values
of s. Make Normal quantile plots of both sets of data.
Briefly describe each of these distributions. Are they sym-
metric or skewed? Are they roughly Normal? Where are
their centers? (The distributions of measures like x and
s when repeated sets of observations are made from the
same theoretical distribution will be very important in
later chapters.)
Transcribed Image Text:A market researcher selects a large sample of potential car buyers. For each consumer, she records gender, age, household income, and automobile preference. Which of these variables are categorical and which are quantitative? 1.175 Two distributions. If two distributions have exactly the same mean and standard deviation, must their histograms have the same shape? If they have the same five-number summary, must their histograms have the same shape? Explain. 1.176 Norms for reading scores. Raw scores on behavioral tests are often transformed for easier compari- son. A test of reading ability has mean 70 and standard deviation 10 when given to third-graders. Sixth-graders have mean score 80 and standard deviation 11 on the same test. To provide separate "norms" for each grade, we want scores in each grade to have mean 100 and stan- dard deviation 20. (a) What linear transformation will change third-grade scores x into new scores new = a + bx that have the desired mean and standard deviation? (Use b> 0 to preserve the order of the scores.) (b) Do the same for the sixth-grade scores. (c) David is a third-grade student who scores 72 on the test. Find David's transformed score. Nancy is a sixth-grade student who scores 78. What is her transformed score? Who scores higher within his or her grade? (d) Suppose that the distribution of scores in each grade is Normal. Then both sets of transformed scores have the N(100, 20) distribution. What percent of third-graders have scores less than 75? What percent of sixth-graders have scores less than 75? 1.177 Use software to generate some data. Most statis- tical software packages have routines for generating val- ues of variables having specified distributions. Use your statistical software to generate 30 observations from the N(25, 8) distribution. Compute the mean and standard deviation and s of the 30 values you obtain. How close are x and s to the μ and o of the distribution from which the observations were drawn? Repeat 19 more times the process of generating 30 observations from the N(25, 8) distribution and recording x and s. Make a stemplot of the 20 values of and another stemplot of the 20 values of s. Make Normal quantile plots of both sets of data. Briefly describe each of these distributions. Are they sym- metric or skewed? Are they roughly Normal? Where are their centers? (The distributions of measures like x and s when repeated sets of observations are made from the same theoretical distribution will be very important in later chapters.)
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