Question

An article in Electronic Packaging and Production (2002, vol. 42) considered the effect of X-ray inspection of integrated circuits. The radiation dose (rads) were studied as a function of current (in milliamps) and exposure (in minutes).The data are in excel file uploaded to Moodle. Name of the file is “Assignment 4 Data”. Use a software (preferable MINITAB) to answer the following questions

Part 2. Now, add current to the model and perform multiple regression analysis. (Include the output in your pdf file.)

a) Write the fitted model.

b) Is the model overall significant? Test at significance level of 5%.

c) Is current a significant variable for the model? Test at α=0.05.

d) Use the model to estimate mean radiation dose when the current is 25 mA and exposure time is 30 seconds.

e) Do you observe an improvement in coefficient of determination? Explain

***Assume that you have data of radiation dose, exposure time and mA for 40 samples. Can you solve the problem above using minitab amd show the steps please?

Rads	mA	Exposure Time
7,4	10	0,25
14,8	10	0,5
29,6	10	1
59,2	10	2
88,8	10	3
296	10	10
444	10	15
592	10	20
11,1	15	0,25
22,2	15	0,5
44,4	15	1
88,8	15	2
133,2	15	3
444	15	10
666	15	15
888	15	20
14,8	20	0,25
29,6	20	0,5
59,2	20	1
118,4	20	2
177,6	20	3
592	20	10
888	20	15
1184	20	20
22,2	30	0,25
44,4	30	0,5
88,8	30	1
177,6	30	2
266,4	30	3
888	30	10
1332	30	15
1776	30	20
29,6	40	0,25
59,2	40	0,5
118,4	40	1
236,8	40	2
355,2	40	3
1184	40	10
1776	40	15
2368	40	20

Answer 1

Stat -> regression -> regression

a)
rads^ = -440.4 + 19.15 mA + 68.08 Exposure time

b)
F = 99.67, p-value = 0.0000 < alpha
hence the model is significant

c)
yes, p-value of mA = 0.000 < alpha

d)
rads^ = -440.4 + 19.15 *25 + 68.08*30
= 2080.75

e) R^2 = 79.57 % {compare with previous model)