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STAT 101  Agresti
Homework 1 Solutions (including optional exercises)
9/2/10
1.2. (a) Population was all 7 million voters, and sample was 2705 voters in exit poll. (b) A statistic is the
56.5% who voted for Schwarzenegger from the exit poll sample of size 2705; a parameter is the 55.9%
who actually voted for Schwarzenegger.
1.3. (a) All students at the University of Wisconsin. (b) A statistic, since it’s calculated only for the 100
sampled students.
1.5. (a) All adult Americans. (b) Proportion of all adult Americans who would answer definitely or
probably true. (c) The sample proportion 0.523 estimates the population proportion. (d) No, it is a
prediction
of the population value but will not equal it exactly, because the sample is only a very small
subset of the population.
1.17. (a) A statistic is the 45% of the sample of subjects interviewed in the UK who said
yes
. (b) A
parameter is the true percent of the 48 million adults in the UK who would say
yes
. (c) A descriptive
analysis is that the percentage of
yes
responses in the survey varied from 10% (in Bulgaria) to 60% in
Luxembourg). (d) An inferential analysis is that the percentage of adults in the UK who would say
yes
falls between 41% and 49%.
2.1. (a) Discrete variables take a set of separate numbers for their values (such as nonnegative integers).
Continuous variables take an infinite continuum of values. (b) Categorical variables have a scale that is a
set of categories; for quantitative variables, the measurement scale has numerical values that represent
different magnitudes of the variable. (c) Nominal variables have a scale of
unordered
categories, whereas
ordinal variables have a scale of
ordered
categories. The distinctions among types of variables are
important in determining the appropriate descriptive and inferential procedures for a statistical analysis.
2.2. (a) Quantitative (b) Categorical (c) Categorical (d) Quantitative (e) Categorical (f) Quantitative (g)
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 Fall '10
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