1
Name ________________________ ID# ____________
Lecture section ________ Lab Section #_______
PS296 Assignment 5 Due: Monday April 8
Note: If you do not provide your correct Lab Section above, you will lose 1 point. This assignment, like the previous
assignments, is due at the beginning of class time. If you are late to class, or if you hand it in after the start of class, it
will be marked late; if you have previously submitted an assignment late, the TA will still mark this assignment and
provide feedback, but you will receive a grade of zero for this assignment.
For each calculation question (starting with 1e), you must show the formula used, the
substitution of numbers into the formula, and your final answer (rounded off to two
decimal places).
1a) The data given below represent the age (in years) and asking price (in thousands of
dollars, rounded off) for a sample of 12 used Toyota Corollas (silver exterior, automatic
transmission) advertised in AutoTrader magazine on a randomly chosen day.
Calculate the means of X and Y and complete the calculations in the table, including the
column sums on the bottom row.
Age Price
(X) (Y) (X X ) (Y Y ) (X X ) (Y Y) (X X)(Y Y) X2 Y2 XY
3 19
1 19
1 17
2 16
2 15
4 14
3 14
2 14
4 11
5 10
4 10
5 9
2
1b) On the graph below complete the scatterplot of the Toyotas’ ages (0-5 years) on the X
axis against their asking price (9-20 $K) on the Y axis.
Draw a rough best-fitting straight line through the plot, making sure it passes through
the point X,Y . 3
1c) It appears as if age and asking price are related. Is it a positive or negative linear
relationship? What indicates that it is either positive or negative?
1d) Does it appear to be a strong or weak relationship? Why do you say this?
1e) Using the numbers you’ve computed in 1a), calculate the covariance between X and Y
using the formula found on the bottom of p. 198.
cov =
xy
1f) Calculate the standard deviations of X and Y (s & sx) usyng either of the two formulas
found on

More
Less