Question

1.)The data were fitted to the following multiple linear regression model

y=Bo+B1X1+B2X2

The standard error for the coefficient B1 is equal to (keep two decimal places)

2.) For 99% confidence interval for the coefficient B2 is approximately

3.)What is the mean radiations when the current is 15 milliamps and the exposure time is 5 seconds. (Keep 1 decimal place)

4.)The 95% confidence interval for the increase in the mean radiations when the current is fixed and the exposure time change from 5 seconds to 10 seconds is approximately

5.)What is the standard error for the regression model? (keep one decimal place)

Questions 1-5 are based on the following statement: A study considered the effect of X-ray inspection of integrated circuits.The rads (radiation dose, Y) were studied as a function of current X1(in milliamps) and exposure time X2(in seconds). The data are in the following table (sample size n=40):

Rads	Current	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

The regression analysis is done in excel by following these steps,

Step 1: Write the data values in excel. The screenshot is shown below,

Step 2: DATA > Data Analysis > Regression > OK. The screenshot is shown below,

Step 3: Select Input Y Range: Rads column, Input X Range: Current and Time columns, enter Confidence Level: 99%. The screenshot is shown below,

The result is obtained. The screenshot is shown below,

1)

From the result summary, regression equation is,

Th standard error for is,

2)

Form the result summary, the 99% confidence interval for the coefficient   is approximately ,

3)

Form the result summary, the regression equation is

4)

The difference of two means when current is fixed and exposure time change from 5 sec to 10 sec,

(The t value is obtained using the t distribution table for 99% confidence interval for degree of freedom = 37)

5)

From the result summary,