# Quiz Question 1 at the end of lesson 4.1 of the LSSGB ebook

Discussion in 'Six Sigma' started by _19325, May 12, 2019.

1. ### _19325 Well-Known Member

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Question regarding Quiz Question 1 for Section 5 Analyze Phase, Lesson 2.15 (can be found at the end of lesson 4.1 of the LSSGB ebook):

Question: A team wants to test if a new drug reduced pain in the patients. What would be the Type II error?

a) The new drug really works and team concludes it works

b) The new drug does not work and team concludes it works
c) The new drug really works and team concludes it does not work
d) The new drug does not work and the team concludes it does not work

The correct answer given is C and the explanation is:

Type II error fails to reject the null hypothesis when it is false, therefore, if the null hypothesis is the drug, it does not cause a difference in pain levels.

So the first part of the explanation is the correct definition of type II errors (“Type II error fails to reject the null hypothesis when it is false”), however the second part of the explanation doesn’t make sense and contradicts the first part of the explanation.

The second part of the explanation states that “if the null hypothesis is the drug, it does not cause a difference in pain levels”. Doesn’t this statement define a type I error and not a type II error? A type I error is rejecting a null when it is true and in this case letter C and the second part of the explanation both reject the drug when it is true. Shouldn’t the correct answer be letter B since your team accepts the null (fails to reject null) when the drug should be rejected?

For reference here is the correct definition of each error compared to the provided answers (letter B and C):

Null hypothesis is the drug

Type I error (alpha risk): Rejecting null when null is true.
Answer C: The new drug really works and team concludes it does not work

Type II error (beta risk): Accepting null when null is false.
Answer B: The new drug does not work and team concludes it works

Can someone please clarify this for me.

#1
Last edited: May 12, 2019
2. ### Vishesh_8 Well-Known Member

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The link has been shared with our trainer Urmimala. I will update once it is done

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3. ### _19325 Well-Known Member

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Any update on this?

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4. ### _33394 Member

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If one draw matrix Team reaction V/s Patient reaction for Drug Reduces pain and Drug Does Not Reduces pain as given in 4.1 page 10,
it can be easily identified as Type -II error is false negative as
1.Team conclude -Drug does not works(false) &
2.Patients conclude- it does work(Negative)
Please correct me If I am wrong.

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Last edited: Jul 20, 2019
5. ### _19325 Well-Known Member

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OK what exactly is Null? Does Null mean the drug works? Aren't we testing if it is a pass or fail, making Null = pass? If so, see the comparison I made below:

Type I error (alpha risk): Rejecting null when null is true.
Answer C: The team concludes it does not work when the new drug really works

Type II error (beta risk): Accepting null when null is false.
Answer B: The team concludes it works but the new drug does not work

#5
Last edited: Jul 22, 2019
6. ### _33394 Member

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Please see file attached with my understanding

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File size:
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7. ### _19325 Well-Known Member

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I just reread your post and its incorrect. A type II error means a defective product is accepted as effective by the quality assurance team. What you are stating is a type I error or rejecting the product when it is not defective.

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