AnswersNC-Math 4Sampling Distributions – Center and Variability

Sampling Distributions – Center and Variability Answers

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The owner of an apple orchard knows that the average weight of Granny Smith apples is 380 grams. A random sample of 40 apples was selected, and the mean weight was 390 grams. Let μ = the true mean weight of the Granny Smith apples in the orchard. Under the assumption that the true mean weight of Granny Smith apples is 380 grams, 100 simulated means for samples of size 40 are shown in the dotplot.Using the dotplot, is there evidence that the true mean weight of Granny Smith apples is greater than 380 grams?

Question illustration
A
Yes, since a sample mean weight of 390 grams or more only occurred once in 100 simulated values, there is evidence that the true mean weight is greater than 380 grams.
B
Yes, since a sample weight of 390 grams is greater than the mean weight of 380 grams, there is evidence to prove that the true mean weight of the apples is greater than 380 grams.
C
No, since a sample mean weight of 390 grams is only 10 grams more than a mean weight of 380 grams, there is insufficient evidence that the true mean weight of the apples is greater than 380 grams.
D
No, since a sample mean weight of 390 grams never occurred in the dotplot, it is not possible that a random sample of 40 apples will have a mean weight of 390 grams. Therefore, there is insufficient evidence that the true mean weight is greater than 380 grams.
4

A farmer determines that, on average, his chickens lay a total of 16 eggs each day. A random sample of 10 days was taken, and the mean number of eggs was 15.1 eggs. Let μ = the true mean number of eggs the chickens lay each day. Under the assumption that the true mean number of eggs is 16, 100 simulated means for samples of size 10 are shown in the dotplot.Using the dotplot, is there evidence that the chickens are laying fewer than 16 eggs?

Question illustration
A
Yes, since a sample mean number of eggs of 15.1 eggs or less only occurred twice in simulated values, there is evidence that the true mean number of eggs is less than 16.
B
Yes, since a sample mean number of eggs of 15.1 is less than the mean number of eggs of 16, there is evidence to prove that the true mean number of eggs is less than 16.
C
No, since a sample mean number of eggs of 15.1 is only 0.9 eggs less than a mean number of eggs of 16, there is insufficient evidence that the true mean number of eggs is less than 16.
D
No, since a sample mean number of eggs of 15.1 never occurred in the dotplot, it is not possible that a random sample of 10 eggs will have a mean number of eggs of 15.1. Therefore, there is insufficient evidence that the true mean number of eggs is less than 16.
5

A student decides to spin a dime and determine the proportion of times it lands on heads. The student spins the dime 25 times and records that it lands on heads 17 times. He decides to spin the dime again and spins it 100 times. Which of the following is a correct statement about the variability of the sampling distribution?

A
Since the sample size is increased, the variability will increase.
B
Since the sample size is increased, the variability will decrease.
C
Since the sample size is increased, the variability of the population will increase.
D
Since the sample size is increased, the variability of the population will decrease.
6

A statistics teacher has a large container of beads that she says contains 60% blue beads. A student randomly selects 50 beads. Let p = the true proportion of blue beads in the container. Under the assumption that the true proportion is 0.60, the student generated 200 values of .What does the dot above 0.74 represent?

Question illustration
A
There is a 1 in 200 chance that the true proportion of blue beads is 0.74.
B
In one simulated sample of 50 beads the proportion of blue beads is 0.74.
C
There is a 1 in 200 chance that the sample proportion of blue beads is 0.74.
D
In one simulated sample of 50 beads the true proportion of blue beads is 0.74.
7

The ages of the 5 officers for a school club are 18, 18, 17, 16, and 15. The mean of the ages of the officers is 16.8. The table displays all possible samples of size 2 and the corresponding mean for each sample.Using the means in the table, is the sample mean an unbiased estimator?

Question illustration
A
Yes, 50% of the sample means are above 16.8 and 50% are below.
B
Yes, the mean of the sample means is 16.8, which is the same as the mean age of the officers.
C
No, it is not possible to determine if the sample mean is an unbiased estimator.
D
No, none of the sample means was 16.8; the sample mean is not an unbiased estimator.
8

The owner of an apple orchard knows that the average weight of Granny Smith apples is 380 grams. A random sample of 40 apples was selected, and the mean weight was 390 grams. Let μ = the true mean weight of the Granny Smith apples in the orchard. Under the assumption that the true mean weight of Granny Smith apples is 380 grams, 100 simulated means for samples of size 40 are shown in the dotplot.What does the dot above 371 represent?

Question illustration
A
The majority of the samples of Granny Smith apples had mean weights greater than 371 grams.
B
In one simulated random sample of 40 Granny Smith apples, the mean weight of the sample was 371 grams.
C
In one simulated random sample of 40 Granny Smith apples, the mean weight of the population was 371 grams.
D
There is a 1 out of 100 chance that a random sample of 40 Granny Smith apples will have a mean weight of 371 grams.

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