STAT 201:23
Assignment 2 on 2.7, 3.1, 3.2, 3.3 and 3.4
The following questions are to be answered and handed in (on
paper) by the end of class on Wednesday, February 3. This is a long
assignment, so dont leave it until the night before!! For the
question involving SPSS, you can get information about SPSS in the
textbook or from Google. The last 20-30 minutes of class on Monday
February 3 will be devoted to answering questions about SPSS (or
other questions about the assignment). It is not mandatory to stay
if you dont need help.
1. (2.108 page 98) Consider the boxplot shown.
(a) What is the median of the data set (approximately)?
(b) What are the upper and lower quartiles of the data set
(approximately)?
(c) What is the interquartile range of the data set
(approximately)?
(d) Is the data set skewed to the left, skewed to the right, or
symmetric?
(e) What percentage of the measurements in the data set lie to
the right of the median? To the left of the upper quartile?
(f) Identify any outliers in the data.
2. (2.118, page 100) Network server downtime. A manufacturer of
network computer server systems is interested in improving its
customer service support services. As a first step, its marketing
department has been charged with the responsibility of summarizing
the extent of customer problems in terms of system downtime. The 40
most recent customers were surveyed to determine the amount of
downtime (in hours) they had experienced during the previous month.
These data are listed in the table.
(a) Construct a box plot for these data. Use the information
reflected in the box plot to describe frequency distribution of the
data set. This description should address central tendency,
variation, and skewness.
(b) Use your box plot to determine which customers are having
unusually lengthy downtimes.
(c) Find and interpret the z-scores associated with the
customers you identified in part (b).
3. (3.6, page 140) Two fair dice are tossed, and the face on
each die is observed.
(a) Use a tree diagram to find the 36 sample points contained in
the sample space.
(b) Assign probabilities to the sample points in part (a).
(c) Find the probability of each of the following events:
A={3 showing on each die}
B={sum of two numbers showing is 7}
C={sum of two numbers showing is even}
4. (3.24, page 143) Highest-rated new cars. Consumer Reports
magazine annually asks readers to evaluate their experiences in
buying a new car during the previous year. Analysis of the
questionnaire for a recent year revealed that readers were very
satisfied with the following three new cars (in no particular
order): Hyundai Elantra, Toyota Prius, and Subaru Forrester.
(a) List all possible sets of rankings for these top three
cars.
(b) Assuming that each set of rankings in part (a) is equally
likely, what is the probability that the readers ranked Toyota
Prius first? That readers ranked Hyundai Elantra third? That
readers ranked Toyota Prius first and Subaru Forrester second?
5. (3.40, page 153) Social networking web sites in the UK. In
the US, MySpace and Facebook are considered the two most popular
social networking sites. In the UK, the competition for social
networking is between MySpace and Bebo. According to
Neilson/NetRatings, 4% of UK citizens visit MySpace, 3% visit Bebo,
and 1% visit both MySpace and Bebo.
(a) Draw a Venn diagram to illustrate the use of social
networking sites in the UK
(b) Find the probability that a UK citizen visits either the
MySpace or Bebo social networking site
(c) Use your answer to (b) to find the probability that a UK
citizen does not visit either social networking site
6. The data for this exercise will be generated by you, and the
point of this exercise is to get experience with SPSS. You just
need two different (so a nickel and dime for example) fair coins
(equally likely to get heads or tails). Heads will be given the
value of 1, and tails will be given the value of 0. You will toss
the coins 20 times and record the result for each, using SPSS:
(a) Open SPSS. Go to Variable View. Create the following
variables: coin_type, coin_1, coin_2, total. For each variable,
select a type. For Numerical data, select Numeric with 0 decimal
places and under Measure, select scale. If it is non-numerical,
select the data type to be string. Total is a numerical variable.
Label each coin as Coin 1 or Coin 2. The Role of each variable may
be set to Input.
(b) For the variable coin_type, click under the Values heading.
Create a value for your type of coin. If you used a nickel, under
Value use N and Label use Nickel, etc.
(c) Return to Data View. Fill in the values that you recorded
for each of your 20 tosses.
(d) Use SPSS to calculate the total of the two coins you tossed
for each trial. To do this in the Transform menu, click Compute
Variable. Target Group is Total. It is up to you to figure out the
appropriate Numeric Expression to calculate the sum of the two
coins (possible values are 0+0=0, 1+0=1, 0+1=1, or 1+1 =2).
(e) Compute the minimum, maximum, mean and standard deviation of
Coin 1, Coin 2, and the Total in one table. To do this, look under
the Analyze Menu, Descriptive Statistics and select Descriptive.
Copy and paste this into a word document.
(f) Figure out how to make a histogram out of your Total column.
Copy and paste this into a word document.
Good practice questions from the book (not to be handed in,
answers in back of book):
2.109, 2.111, 2.115, 2.135, 3.1, 3.3, 3.5, 3.7, 3.11, 3.13,
3.31, 3.33, 3.35, 3.41, 3.43
