Chapter 5 Probability Distributions 221
function returns the value of x. Use this
function to calculate the x values for the
following:
a. mean 5 5, std_dev 5 2, prob 5 .10
b. mean 5 5, std_dev 5 2, prob 5 .20
c. mean 5 5, std_dev 5 2, prob 5 .50
d. mean 5 5, std_dev 5 2, prob 5 .90
e. mean 5 5, std_dev 5 2, prob 5 .95
f. mean 5 5, std_dev 5 2, prob 5 .99
- Open the Baseball workbook from the
Chapter05 folder. You want to analyze
the batting average statistics from the
workbook. The mean career batting aver-
age is .263 and the standard deviation is
.02338.
a. Open the workbook and save it as
Batting Average Analysis.
b. Assuming that the batting averages
are normally distributed, use Excel’s
NORMDIST function to fi nd the prob-
ability that a player will bat .300 or
better. (Hint: Calculate 1 2 probability
that a player will bat less than .300.)
c. How many players batted .300 or
better? Compare this to the expected
number.
d. Save your workbook and summarize
your fi ndings.
- The Housing workbook contains a
sample of 117 housing prices for
Albuquerque, New Mexico, during the
early 1990s. You’ve been asked to
analyze this historic data set.
a. Open the Housing workbook from
the Chapter05 folder and save it as
Housing Price Analysis.
b. Create a histogram (with a normal
curve) and a normal probability
plot of the housing prices. Do the
data appear to follow a normal
distribution?
c. Calculate the average housing price
and the standard deviation of the
housing price. Because this is a
sample of all of the house prices in
Albuquerque, the average serves as an
estimate of the mean house price.
d. Create a new column containing the
log of the home price values. Create a
histogram with a normal curve and a
normal probability plot. Modify the
x axis label Number format to display
the log values to three decimal places.
Do the transformed values appear
more normally distributed than the
untransformed values?
e. Save your changes to the workbook.
Write a report summarizing your
observations and calculations.
- The dispersion of shots used in shoot-
ing at the target in the Random Samples
workbook follows a bivariate normal
distribution (a combination of two nor-
mal distributions, one in the vertical
direction and one in the horizontal
direction). The value of s for each level
of accuracy is
Accuracy Standard Deviation
Highest 0.1
Good 0.2
Moderate 0.4
Poor 0.6
Lowest 1.0
a. Open the Random Samples workbook
from the Explore folder and create a
distribution of shots around the target
with good accuracy.
b. Explain why the predicted percent-
ages have the values they have.
c. For a shooter with the lowest ac-
curacy, how many shots would the
person have to take before she or he
could assume with 95% confi dence
