The corrosive effects of various soils on coated and uncoated steel pipe was tes
ID: 3132745 • Letter: T
Question
The corrosive effects of various soils on coated and uncoated steel pipe was tested by using a dependent sampling plan. The data collected are summarized below, where d is the amount of corrosion on the coated portion subtracted from the amount of corrosion on the uncoated portion. Does this random sample provide sufficient reason to conclude that the coating is beneficial? Use = 0.01 and assume normality.
n = 40, d = 222, d2 = 6133
(a) Find t. (Give your answer correct to two decimal places.)
(ii) Find the p-value. (Give your answer correct to four decimal places.)
Explanation / Answer
Given
N=40
sigma(d)=222
sigma(d2)=variance=6133
standard deviation
=sqrt(variance)= 78.313
standard error
=standard deviation/sqrt(n)
=78.313/sqrt(40)
=12.38
t-value
mean/standard error
=222/12.38
=17.9
for 0.01 significance level ,df =19 ,
p-value is approximately tends to 0 (very small value)