Solutions to Homework Assignment #1
Statistics 220, Fall 2005
Due September 7, 2005
1.10
a
The stem-and-leaf plot should look something like this.
5|9
6|33588
7|00234677889
8|127
9|077
10|7
11|368
Wha
Solutions: Assignment 10
November 23, 2005
12.4
0
20
40
60
80
100
120
140
a.
x
y
Figure 1: boxplot for 12.4
There are a couple of interesting features. First, we see that both x and
y have outliers. 2
Solutions to Homework #9, 36-220
Due 16 November 2005
8.54
We are supposed to test whether the true average percentage of organic matter
in such soil is something other than 3%. So our null hypothesis
36-220 Engineering Stats, Fall 2005
Homework 8 Solutions
Due: November 9, 2005
Exercise 8.4
We consider these two hypothesis tests:
H0 :
H1 :
Test 1
=5
>5
Test 2
=5
<5
A desirable hypothesis test keep
Solutions: Assignment 7
November 1, 2005
N.D. 1
a.
X bin(n, p)
E [X ] = np
V (X ) = np(1 p)
E [] = E [
p
X
1
] = E [X ]
n
n
1
[np] = p
n
Bias = (E [] p) = p p = 0
p
=
b.
X
1
1
) = 2 V (X ) = 2 (np(1 p
Solutions to Homework #6, 36-220
Due 12 October 2005
Non-Devore Problem
The rule for variances which says Var (X + Y ) = Var (X ) + Var (Y ) only applies
if X and Y are uncorrelated random variables,
36-220 Engineering Stats, Fall 2005
Homework 5 Solutions
Due: October 5, 2005
Non-Devore Exercise
Let T be an exponential random variable that represents the time until a radioactive atom decays
and b
Solutions to Homework Assignment #3
Statistics 220, Fall 2005
Due September 21, 2005
2.52
Let A1 = pump #1 fails, and A2 = pump #2 fails. Because the pumps are
identical, we can assume that Pr (A1 ) =
Solutions to Homework Assignment #2
Statistics 220, Fall 2005
Due September 14, 2005
The following formula is true for any two events A and B , and is useful in
several problems:
P (A B ) = P (A) + P