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xliu1
Quartz | Level 8

I am reviewing the practice questions for SAS Interactive Model Building using SAS Visual Statistics 8.4 on SAS Viya, and I am quite confused by correct answers for these two questions:

Q1:

xliu1_0-1644966812283.png

In my opinion, B and D are not linear while A and C are linear

Q2:

xliu1_1-1644966957910.png

I think D should be the correct one.

Just want to post here to get confirmation on these very basic concepts. Or am I not reading these questions correctly?

 

1 ACCEPTED SOLUTION

Accepted Solutions
MarkusWeick
Barite | Level 11

Hi @xliu1

concering Q1: I think you are rigth. The X as the Variables are linear in answer A. and C. 

Concerning Q2: I think you are wrong.

The expession of the linear regression would be .... - 0.3696 x RunPulse + ... .

So a one unit decrease in RunPulse would lead to a 0.3696 increase in the response and not vice versa.

Hope, this helps.

Best, Markus

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6 REPLIES 6
MarkusWeick
Barite | Level 11

Hi @xliu1

concering Q1: I think you are rigth. The X as the Variables are linear in answer A. and C. 

Concerning Q2: I think you are wrong.

The expession of the linear regression would be .... - 0.3696 x RunPulse + ... .

So a one unit decrease in RunPulse would lead to a 0.3696 increase in the response and not vice versa.

Hope, this helps.

Best, Markus

Please keep the community friendly.
Like posts you agree with or like. Mark helpful answers as “accepted solutions”. Generally have a look at https://communities.sas.com/t5/Getting-Started/tkb-p/community_articles
xliu1
Quartz | Level 8

@MarkusWeick Thank you for your response. Now I can see the wording is wrong for option D. But their correct answer C is not right. For one-unit increase in RunTime, should there be expected 2.6287 decrease in response as the equation follows102.9345+...-0.36963*RunPulse-2.62865*RunTime...? 

MarkusWeick
Barite | Level 11

@xliu1: I agree with you. It seems to be a typo.

Please keep the community friendly.
Like posts you agree with or like. Mark helpful answers as “accepted solutions”. Generally have a look at https://communities.sas.com/t5/Getting-Started/tkb-p/community_articles
Mark2010
SAS Employee

OK, so the run pulse increase/decrease is a typo and will be changed to decrease. My apologies for this.

 

But on the linear model question, the answer C is correct. I had a consult with one of our stats instructors, and here is the scoop:

The linearity of the model is based on the structure of the parameters (the b's) and not the predictors (the X's). The X1X2 and X3 (sorry, I can't do subscripts and superscripts here) will give us a linear model with non-linear effects. The division element in answer choice C (b2/b1) is the part that causes the non-linearity in the model. 

MarkusWeick
Barite | Level 11

@Mark2010: Thanks. Now I see, that you are right. I consulted one of my text books.

@xliu1Linear model - Wikipedia is a good short presentation, which shows different uses of linear in different statistical contexts.

Please keep the community friendly.
Like posts you agree with or like. Mark helpful answers as “accepted solutions”. Generally have a look at https://communities.sas.com/t5/Getting-Started/tkb-p/community_articles
xliu1
Quartz | Level 8

Thanks all for quick responses and sharing the link. It clears up my confusion. Very much appreciated!

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