Homework 2: Due Sept 19th
1.
A development engineer is interested in determining if varying the cotton content in a synthetic fiber
affects the tensile strength. To do the study he randomly picks 5 swatches of cloths from 5 different
types of processes (with varying amounts of cotton in them). He puts the swatches randomly through a
stress test and observes the tensile strength (the force at which the cloth tears). Here is the data:
% Cotton
15
20
25
30
35
2.
7
12
14
19
7
Observed Tensile Strength
7
15
17
12
18
18
25
22
10
11
11
18
19
19
15
It is of interest to see if the Soil Electrical Conductivity affects tomato yields. A Study was designed to
grow 4 plots of tomato plants at the chosen EC levels of 1.6, 3.8, 6.0, and 10.2 nmhos/cm. The given
observations are tomato yields (kg/plot) for four different levels of electrical conductivity (EC) of the soil.
EC level
1.6
3.8
6.0
10.2
59.5
55.2
51.7
44.6
53.3
59.1
48.8
48.5
Yield
56.8
52.8
53.9
41.0
63.1
54.5
49.0
47.3
For the data in 1 and 2 above give:
a.
b.
c.
d.
9
18
19
23
11
The ANOVA table and comment of the F-test
Discuss the assumptions of normality, equal variance and independence
If the F-statistic is rejected follow up with a TUKEY and LSD multiple comparisons.
Summarize your findings and write your conclusions.