___
X
___ Correct
_______ Incorrect
ii.
With 99% confidence, it can be suggested that on average, in the population of all words, the words in
Spanish
are
between
1.7427
characters
shorter
and
0.1627
characters
longer
than
their
corresponding equivalents in Russian.
___
X
___ Correct
_______ Incorrect
iii.
The probability that the population mean difference in the number of characters between words in
Spanish and their corresponding equivalents in Russian (Spanish – Russian) for the population of all
words is between -1.7427 and 0.1627 characters is 0 or 1.
___
X
___ Correct
_______ Incorrect
alternative hypothesis:
true difference in means is not equal to 0
99 percent confidence interval:
-1.7427
0.1627
sample estimates:
mean of the differences
-0.79
mean
sd
se(mean)
Spanish
7.32
2.1736
0.21736
Russian
8.11
3.5388
0.35388
Difference -0.79 3.627323 0.36273
100
n
100
100

3.
Yellow (Maize) Car? ~
A loyal Michigan fan currently has a blue car. He plans to purchase a brand-new car and
is considering a yellow car. He wonders if purchasing a brand-new yellow car will hurt his ability to sell the car
in the future, say in three years. He decides to do some research about the average number of days it takes to
sell a three-year-old yellow car. The stated average number of days it takes to sell a three-year-old car of any
color is 30 days. He obtains a random sample of 40 yellow three-year-old cars up for sale and records the
number of days it takes to sell each car. He would like to use these results to assess if yellow cars take longer
to sell on average compared to that for three-year-old cars of any color, at the 5% level of significance.
a.
This loyal Michigan fan expressed the hypotheses for the test as shown:

[2]
Briefly explain why these are not the correct hypotheses to be tested?

b.
Suppose the average number of days it takes to sell a three-year-old yellow car really is 30 days. If we
were to repeat this study 60 times, each time taking a random sample of 40 yellow three-year-old cars up
for sale and conducting the same appropriate hypothesis test at the same significance level, then
how
many
decisions would we expect to be incorrect?

Stats 250 Fall 2017 Exam 2
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