University of Minnesota, Twin Cities
School of Statistics
Stat 3011
Rweb
Textbook (Wild and Seber)
Stat 3011 (Geyer) First Midterm (Computer Lab Part)
Go to question:
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General Instructions
The exam is open book, open web pages. You may use the computer,
a calculator, or pencil and paper to get answers, but it is expected
that you will use the computer. Show all your work:
- For simple computer commands, you may just write the command
you used and the result it gave on this test form.
- For complicated commands or plots, make a printout and attach
the printout to the test form (we'll provide a stapler).
No credit for numbers with no indication of where
they came from!
Suppose a random variable X has a normal distribution with
mean 250 and standard deviation 50.
- Find the probability that X is greater than 325.
- Find the probability that X is between 200 and 275.
- Find the the 35th percentile of the distribution of X
You may use the form below to answer this question.
The file t1.dat contains a single variable
named fred for which measurements on 200 individuals are recorded.
- Draw some sort of plot that shows you the shape of the distribution
of the data.
(Hand in this plot. Be sure to put your name on the plot
before sending it to the printer. Either put your name in quotes as one
command or add the optional argument
main="your name here" to any
plot command.)
- Describe the shape of the distribution. Is it symmetric or skewed?
If skewed, which way? Is it unimodal or multimodal? Are there any outliers?
- Find the mean.
- Find the median.
- Find the standard deviation.
- Find the interquartile range.
- If you had to pick one measure of center and one measure of spread from
the four numbers just calculated, which would you pick? Explain. Make it
clear which is the measure of center and which is the measure of spread.
The form below automatically loads this data set
t1.dat (like the lecture section
examples). You don't need to anything to load the data.
The distribution of ACT composite scores for all
students taking the test in the year 2000 was normal with mean 21.0 and
standard deviation 4.7.
Suppose you had a composite score of 31. What fraction of the students
taking the test did you do better than? What fraction did you do worse than?
You may use the form below to answer this question.