QNT 275 Week 4 Practice: Week 4 Discussion


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QNT 275 Week 4 Practice: Week 4 Discussion


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QNT 275 Week 4 Practice: Week 4 Discussion
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Review˙the˙Discussion FAQs Module.

Reference˙the Week 3 Case Study.

Respond˙to one of the following:

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Regarding requirement #2: What does the mean and standard deviation mean in terms of expected sales?
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Regarding requirement #2: How can this information be used to benefit the business?
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Regarding requirement #3: Can you conclude whether the data is normally distributed?
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Regarding requirement #4: What can be interpreted by that percentage?
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One-sided test vs. two-sided test
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Hi Class,
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Let me talk a little bit about˙one-sided and two-sided tests (note I use ?side? and ?tail? interchangeably sometimes ? they mean the same thing).˙˙ Whether the test or hypothesis should be one-sided (left or right) or two-sided depend on what we are interested in, i.e the˙research question.˙ It is against the statistical principal if one looks (peeks) at the data and then determine the hypothesis, or the test statistics.
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For example, we are interested in if replacement with new appliances in the house can increase the house price (this is the research question), then the hypotheses are:
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H0:˙ Replacement of new appliances will not increase house selling price
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˙˙˙˙˙˙˙ Or price increment<=0
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H1:˙ Replacement of new appliances will increase house selling price
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˙˙˙˙˙˙˙ Or price increment 0
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This is a right-sided test, because in our research question, we don?t think (or care) that replacement of new appliances would have negative impact on the house price.
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For another example, we are interested in seeing if boys and girls have similar performance in the spelling test in a school.˙ Some people might think girls are better, some might think the other way.˙ So it?s better to have a two-sided test:
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H0:˙ boys? average score = girls? average score
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H1:˙ boys? average score < girls? average score
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As a result we found out girls did better, but to plan a study in the beginning, it?s probably more appropriate to use a two-sided hypothesis.
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How do we know it?s one-sided or two sided, the cue is in the ALTERNATIVE.
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If there is a ?? sign, it?s one-sided and right-tailed test
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If there is a ?
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If there is an unequal sign ?
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Hypothesis Testing

Class, this week, we are jumping into one of the two things the inferential statistics is about :˙ hypothesis testing. ˙(the other one is estimation)

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There are some new terms that we need to get familiar with. ˙Let?s start with null and alternative hypotheses:

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The null and alternative hypotheses put the research/business question in a form of statement so that they can be either ?rejected? or ?not rejected? with a statistical hypothesis testing. ˙The null and the alternative

should be mutually exclusive.˙ Sometimes people get confused about which statement they should put in the null hypothesis (H0) and the ?opposite? in the alternative hypothesis (H1).˙ In researches and business, it is the common practice that we put what we hope to prove/see in the alternative hypothesis statement.˙ For example:

If the research question is ?Is the drug effective??˙ then we use

H0:˙ The drug is not effective

H1: The drug is effective

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?Would advertising increase retail sales?? then

H0: Advertising does not increase retail sales

H1: Advertising increases retail sales

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?Does the new teaching method improve Spanish score in students??

Then

H0:˙ The new method does not improve Spanish score in students.

H1:˙ The new method improves Spanish score in students

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It?s sort of like we would like to look for alternatives ? ?Change is always good? ?

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Class, please feel free to chime in your thoughts!

QNT 275 Week 4 Practice: Week 4 Discussion

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