AnswersVA-Probability and StatisticsScope of Inference

Scope of Inference Answers

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1
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When is it appropriate to make inferences about a population based upon data collected from a sample?

A
when the sample is selected at random from the population of interest
B
any time an experiment is conducted
C
any time an observational study is conducted
D
when a sample is selected from the population of interest
2
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When the students select their random samples and plot the results on a dotplot, which of the following should they expect to see?The dots, which represent the sample proportions obtained by the students,

A
will all be at the same number.
B
will be wildly unpredictable.
C
will be clustered around 0 and 1.
D
will be centered around p, the true population proportion.
3

If the students were to increase the sample size to n = 200 pieces of marbles each, what will the effect be on the center and variability of the sampling distribution?

A
The center would remain about the same. The variability would increase.
B
The center would remain about the same. The variability would decrease.
C
The center would decrease. The variability would increase.
D
The center would increase. The variability would decrease.
4

The manager of the marbles store wants to increase the precision of the estimate of the true mean dollar amount of all purchases made by customers at his store that day.Which sample size will give the manager the greatest precision of the estimate of the true mean dollar amount of all purchases made by customers at his store that day?

A
20
B
30
C
40
D
50
5

When are the results of an experiment said to be statistically significant?

A
when the experimental design uses the principles of randomization, control, comparison, and replication
B
when the results from each treatment group differ
C
when a large sample size is used in each treatment group
D
when the observed results of a study are too unusual to be explained by chance alone
6

Mrs. Miller claims that 10% of the marbles in the jar are purple. Do the students have statistically significant evidence that the true proportion of purple marbles in the jar is greater than 10%? Use the sampling distribution to help answer the question.

A
No, = 0.22 or greater occurred in 8% of samples in the simulation. Because this is greater than 5%, they do not have statistically significant evidence that the true proportion of purple marbles in the jar is greater than 10%.
B
No, = 0.22 or greater only occurred in 1% of samples in the simulation. Because this is not greater than 5%, they do not have statistically significant evidence that the true proportion of purple marbles in the jar is greater than 10%.
C
Yes, = 0.22 or greater only occurred in 1% of samples in the simulation. Because this is less than 5%, they have statistically significant evidence that the true proportion of purple marbles in the jar is greater than 10%.
D
Yes, = 0.22 or greater occurred in 8% of samples in the simulation. Because this is less than 5%, they have statistically significant evidence that the true proportion of purple marbles in the jar is greater than 10%.
7

For which of these studies can we draw conclusions of cause and effect?

A
A
B
B
C
C
D
None of them
8

The valid conclusion is .

A
A only
B
B only
C
A and B
D
Neither A or B

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