Stats - W5

Q # 1

Cadmium Contamination Discussion Forum

Truckloads of waste contaminated with cadmium may either be sent to a sanitary landfill or a hazardous waste landfill. The levels of cadmium vary daily so each morning a sample of truckloads must be tested to determine which landfill to use. If the mean level of cadmium exceeds the allowable amount of 1 milligram per liter for a sanitary landfill then the trucks must be sent further to the hazardous landfill. Of course, driving a further distance requires more expense for the company. You are in charge of testing and determining which landfill to use for dumping for today.

You will use a 5% level of significance for your hypothesis test.

1. State the null and alternative hypotheses, and identify which represents the claim. Why?

2. Determine the type of test that you should use: left-tailed, right-tailed, or two-tailed. Explain your reasoning.

3. What sampling technique would you use to determine your sample of truckloads that will be tested this morning? Should a small sample or a large sample be used? Does it really matter?

4. What decision concerning your null hypothesis would result in a Type I error? What is the interpretation and the implication of this error? What about a Type II error? Obviously, you want to minimize the risk of both types of error when decision making. Which of these errors is more serious in this situation?

5. Suppose that the null hypothesis is rejected when you perform your hypothesis test. Assuming that a correct decision was made, what do you believe regarding the mean level of cadmium on today's truckloads? Give a complete interpretation.

Q # 2

Cola Taste Test Discussion Forum

As a class, completely answer the four exercises that are posed. Different students may answer different parts, and the same parts may initially be answered by more than one student, but ultimately (through your discussion), you should talk through all the exercises and work out all the answers to the stated questions. Be sure to restate the exercise that you are answering so that anyone who enters the discussion has a clear frame of reference.

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Forum Posts by other students (This is an active question… So this time: Answer Q # 2, then respond to these three students.)

New Post by Imani Hodges

Re: Cola Taste Test Discussion Forum

1(a) When PepsiCo performed this challenge, PepsiCo representatives went to shopping malls to obtain their sample.  Do you think this type of sampling is representative of the population?  Explain.

I don’t think this type of sampling is representative of the population.  Pepsi only went to shopping malls to conduct the survey.  That means that they only people who could participate were mall shoppers.  Not everyone is a mall shopper.  Admittedly though, it is hard to get a sample representative of the American population because we are so diverse.  However, just visiting one type of establishment targeting one type of consumer is definitely not representative of the larger American population.

New Post by Chris Johnson

1 day ago

Re: Cola Taste Test Discussion Forum

I am going to start with #3 & #4.

#3   I would think that knowing the brand might influence the test participants choices. I personally prefer Coke over

Pepsi. I am not sure if it is a brand labeling issue but it is possible because I know that I don't care for Pepsi. 

#4a  PepsiCo used a blind taste test because the participants wouldn't be able to go into the test influenced by their personal preference that they already have for Pepsi or Coke. A blind taste test puts brand name and preference aside and focuses on pure flavor.

#4b  I believe that taste has more influence because ultimately, people want to drink what tastes good to them, regardless of brand.

#4c  Besides taste and branding, other factors that may influence consumer preferences are: age, occupation, economic situation, personality, and social/cultural background.  

New Post by Debbie Fair

19 hours ago

Re: Cola Taste Test Discussion Forum

1. How would you do it?

(a) When PepsiCo performed this challenge, PepsiCo representatives went to shopping malls to obtain their sample. Do you think this type of sampling is representative of the population? Explain.

- This is not a completely representative sample of consumers, depending on how many shopping       malls and the locations in which they carried out these surveys. The amount of individuals who shop at a mall on a particular day may not be the best representation of a population. Not all people shop at malls and the majority of people will not be at that mall.

(b) What sampling technique would you use to select the sample for your study?

- If it were up to me, I would conduct a survey at a grocery store to see which type of cola the people were purchasing and the type that they prefer. This way, I would know for certain that they did indeed drink cola and that they did prefer a certain brand. I also think that the cola that is the leader in the market would be the most preferred, as it is obviously the brand that is bought most often.

(c) Identify possible flaws or biases in your study.

- My study has somewhat of the same issue as the test at the mall. Not everyone will be at a grocery store. Also, testing those who are already consumers of a certain brand may have brand preference already. 

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