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Questions and Answers

(159 solutions)

nalyses were run. The following is the (edited) output for the test:

Hypothesis Test Results

μ1: Dance Scores: Coached Previously

μ2: Dance Scores: Not Coached Previously

Difference

Sample Mean

Std. Err.

DF

T-Stat

 P-Value 

μ1 - μ2

.11

0.67168

94.155815

0.163767

0.4351

From the output we learn that:

the data do not provide sufficient evidence to reject H0; thus, we cannot conclude that the mean score of the students coached is higher than that of students never coached.Correct! Since the P-value is greater than .05, we fail to reject the null hypothesis and, therefore, cannot conclude that the ...

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Do dance coaches score students that they have previously taught higher at competitions due to bias? Two samples were randomly selected from the British Ballroom competitive circuit. The first sample consisted of 50 students that had been previously trained by a prominent dance coach and judge and the second sample were 50 students who had been trained at a rival dance studio. The total score for each student was calculated to find a mean for each group.

If µ1and µ2 represent the mean dance scores for each group respectively for self-coach vs. rival coached, which of the following is the appropriate pair of hypotheses in this case?

H0:μ1=μ2 Ha:μ1>μ2Correct! Since you want to see if the mean score is higher for the couples that took the partner-blame questionnaire, the alternative hypothesis is: Ha:  μ1 > μ2....

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In a study of the impact of eating fruit on birth weight, researchers analyze birth weights (in grams) for babies born to 189 women who gave birth in 2018 at a hospital in California. Suppose in the group, 74 of the women were categorized as “fruit eaters” and 115 as “non-fruit eaters.” The difference in the two sample mean birth weights (fruit eaters minus non-fruit eaters) is 281.7 grams and the 95% confidence interval is (76.5, 486.9)

Which gives the best interpretation of what we can conclude about the impact of eating fruit on birth weight?

Eating fruit is associated with higher birth weights. When fruit eaters are compared to non-fruit eaters, we are 95% confident that the mean weight of babies of fruit eaters is between 76.5 grams to 486.9 grams more than the mean weight of babies of non-fruit eaters.This study is an observational st...

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College Students and Depression: A public health official is studying differences in depression among students at two different universities. They collect a random sample of students independently from each of the two universities and administer a well known depression inventory. A score of 5 or above indicates some depression. A score above 15 indicates that active treatment is necessary.

Sample Statistics



 Size(n) 

Mean(x¯)

SD(s)

Sample 1

50

9.2

.85

Sample 2

45

8.7

1.2

The official conducts a two-sample t-test to determine whether these data provide significant evidence that students at University 1 are more depressed than students at University 2. The test statistic is t = 2.64 with a P-value 0.005.
Which of the following is an appropriate conclusion?

The samples provide significant evidence that students at University 1 are more depressed than students at University 2.Good job! A P-value this small indicates statistically significant results....

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An advertiser is experimenting with a new color scheme and conducts a study to test its effectiveness. In which situation could they use the two-sample t-test for comparing two population means?

They randomly expose consumers to one website when they land on their page: the old one with the original color scheme or the new one with the updated color scheme. Then they measure to see how much people buy.Good Job! Since participants in this study were randomized to two different groups the dat...

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Suppose the results indicate that the null hypothesis should not be rejected; thus, it is possible that a type II error has been committed.

Given the type of error made in this situation, what could researchers do to reduce the risk of this error?

None of the above...

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Suppose the results indicate that the null hypothesis should be rejected; thus, it is possible that a type I error has been committed.

Given the type of error made in this situation, what could researchers do to reduce the risk of this error?

Change the significance level from .05 to .001This is correct. The most straightforward way to avoid type 1 error is to choose a more conservative significance level. In this case, .001 is the best option to replace .05 because it is the most conservative....

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A manufacturer of a hair dye markets its color as lasting, on average, 200 washes without fading. A consumer group decides to re-test this claim by assessing the number of times that 30 women can wash their hair without the color fading and finds the average is 200.05 washes, with a standard deviation of 1.5.

The resulting p-value is .82588; thus, the null hypothesis is not rejected. The consumer group concludes that the manufacturer’s claim that its hair color lasts, on average, 200 washes is accurate.

What type of error is possible in this situation?

type IIGood job! The statement describes a situation where we fail to reject a false null hypothesis. This could be a type II error....

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A manufacturer of a hair dye markets its color as lasting, on average, 200 washes without fading. A consumer group decides to test this claim by assessing the number of times that 30 women can wash their hair without the color fading and finds the average is 203 washes, with a standard deviation of 5.2.

The resulting p-value is 0; thus, the null hypothesis is rejected. The consumer group concludes that the manufacturer’s claim that its hair color lasts, on average, 200 washes is inaccurate.

What type of error is possible in this situation?

type IThe conclusion here is that the null hypothesis is false but the null hypothesis could actually be true. This would be a type I error....

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Biomedical researchers are testing a cancer treatment to see if it is safe for human use. This can be thought of as a hypothesis test with the following hypotheses.

  • H0: the medicine is safe
  • Ha: the medicine is not safe

The following is an example of what type of error?

The sample suggests that the medicine is not safe, but it actually is safe.

type IGood job! The conclusion here is that the null hypothesis is false but the null hypothesis is actually true. This is a type I error....

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