Posted by **tracy10** on Tuesday, June 25, 2013 at 10:40am.

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 á = 0.01 and assume normality.

n = 48, Ód = 238, Ód2 = 6202

(a) Find t. (Give your answer correct to two decimal places.)

(ii) Find the p-value. (Give your answer correct to four decimal places.)

- math -
**Kuai**, Tuesday, June 25, 2013 at 2:42pm
SSd = 6202 - (238)^2/48

SSd = 5201.917

Sd = sqrt(SSd/n-1)

Sd = sqrt(5021.917/47) =

Sd = 10.337

t = 4.958/10.337/sqrt(48)

t = 3.323

Two tail = .0017

right tail = 8.6885e^-4

Left tail = .9991

- math -
**Tracy 10**, Tuesday, June 25, 2013 at 11:11pm
Have a question, where did you get the 4.958 and what did you look at for it. Thanks this has really helped so far, just unsure on that.

- math -
**Kuai**, Wednesday, June 26, 2013 at 1:57pm
This is mean = 238/48 = 4.985

I am looking for t.

- math -
**Kuai**, Wednesday, June 26, 2013 at 2:17pm
Typo

238/48 = 4.958

- math -
**Tracy**, Wednesday, June 26, 2013 at 4:49pm
But how do you get the p-value, I have worked it out by hand and also put into calculator and it comes up wrong. 0.0017 was the last answer I got. and 0.9991 before that. I have several questions like this asking for p-value so if you could work one out and I could use as an example I would appreciate it. Thank you for all your help. I got the t as 3.32 and that was the right answer on that one.

- math -
**Kuai**, Thursday, June 27, 2013 at 5:16pm
First of all, you have to calculate your mean, standard deviation

sum of d is 238

n is 48

Mean = 238/48 = 4.958

Variance = 6202 -238^2/48 = 5201.92

standard derivation sqrt((variance/n-1)

Sd = 10.337

Find p-value you use your ti-83 plus

Go to stat

Tests

2-T-Test

Enter mean = 4.958

Go to down to Sx then

Standard deviation or sx = 10.337

n =48

Select Not equal

Go to down and select calculate enter

It will you info

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