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COMM 215 > Sampling > Flashcards

Sampling Flashcards

1
Q

Parameters are

A

numerical characteristics of a population

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2
Q

The purpose of statistical inference is to provide information about the

A

population based upon information contained in the sample

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3
Q

From a group of 12 students, we want to select a random sample of 4 students to serve on a university committee. How many different random samples of 4 students can be selected?

A

495

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4
Q

A population consists of 500 elements. We want to draw a simple random sample of 50 elements from this population. On the first selection, the probability of an element being selected is

A

0.002

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5
Q

A population consists of 8 items. The number of different simple random samples of size 3 that can be selected from this population is

A

56

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6
Q

The number of random samples (without replacement) of size 3 that can be drawn from a population of size 5 is

A

10

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7
Q

There are 6 children in a family. The number of children defines a population. The number of simple random samples of size 2 (without replacement) which are possible equals

A

15

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8
Q

The number of different simple random samples of size 5 that can be selected from a population of size 8 is

A

56

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9
Q

How many different samples of size 3 can be taken from a finite population of size 10?

A

120

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10
Q

In point estimation

A

data from the sample is used to estimate the population parameter

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11
Q

The sample mean is the point estimator of

A

(backward u)

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12
Q

The standard deviation of a point estimator is called the

A

standard error

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13
Q

The sample statistic, such as x, s, or p, that provides the point estimate of the population parameter is known as

A

a point estimator

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14
Q

A simple random sample of 5 observations from a population containing 400 elements was taken, and the following values were obtained.
12 18 19 20 21
A point estimate of the mean is

A

18

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15
Q

The following data was collected from a simple random sample of a population. 13 15 14 16 12
The point estimate of the population standard deviation is

A

1.581

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16
Q

The following information was collected from a simple random sample of a population. 16 19 18 17 20 18
The point estimate of the population standard deviation is

A

1.414

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17
Q

If we consider the simple random sampling process as an experiment, the sample mean is

A

a random variable

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18
Q

Sampling distribution of x is the

A

probability distribution of the sample mean

19
Q

A population has a standard deviation of 16. If a sample of size 64 is selected from this population, what is the probability that the sample mean will be within +_2 of the population mean?

A

0.6826

20
Q

The closer the sample mean is to the population mean,

A

the smaller the sampling error

21
Q

As the sample size increases, the

A

standard error of the mean decreases

22
Q

The expected value of the random variable x is

A

not the standard error, the sample size nor the size of a population

23
Q

A population has a mean of 75 and a standard deviation of 8. A random sample of 800 is selected. The expected value of x is

A

75

24
Q

Whenever the population has a normal probability distribution, the sampling distribution of x is a normal probability distribution for

A

any sample size

25
Q

The standard deviation of a sample of 100 elements taken from a very large population is determined to be 60. The variance of the population

A

can be any value greater or equal to zero

26
Q

The probability distribution of all possible values of the sample mean x is

A

the sampling distribution of x

27
Q

A theorem that allows us to use the normal probability distribution to approximate the sampling distribution of sample means and sample proportions whenever the sample size is large is known as the

A

central limit theorem

28
Q

Random samples of size 81 are taken from an infinite population whose mean and standard deviation are 200 and 18, respectively. The distribution of the population is unknown. The mean and the standard error of the mean are

A

200 and 2

29
Q

A population has a mean of 180 and a standard deviation of 24. A sample of 64 observations will be taken. The probability that the sample mean will be between 183 and 186 is

A

0.1359

30
Q

For a population with any distribution, the form of the sampling distribution of the sample mean is

A

always normal for large sample sizes

31
Q

Random samples of size 36 are taken from an infinite population whose mean and standard deviation are 20 and 15, respectively. The distribution of the population is unknown. The mean and the standard error of the mean are

A

20 and 2.5

32
Q

A sample of 92 observations is taken from an infinite population. The sampling distribution of x is approximately

A

normal because of the central limit theorem

33
Q

A population has a mean of 53 and a standard deviation of 21. A sample of 49 observations will be taken. The probability that the sample mean will be greater than 57.95 is

A

.0495

34
Q

Doubling the size of the sample will

A

reduce the standard error of the mean to approximately 70% of its current value

35
Q

As the sample size increases, the variability among the sample means

A

decreases

36
Q

Random samples of size 17 are taken from a population that has 200 elements, a mean of 36, and a standard deviation of 8. Which of the following best describes the form of the sampling distribution of the sample mean for this situation?

A

Not approximately normal because the sample size is small relative to the population size, approximately normal because of the central limit theorem nor exactly normal

37
Q

The following data was collected from a simple random sample of a population.
13 15 14 16 12
The mean of the population

A

could be any value

38
Q

The probability distribution of all possible values of the sample proportion p is the

A

sampling distribution of p

39
Q

A sample of 400 observations will be taken from an infinite population. The population proportion equals 0.8. The probability that the sample proportion will be greater than 0.83 is

A

0.0668

40
Q

Random samples of size 100 are taken from an infinite population whose population proportion is 0.2. The mean and standard deviation of the sample proportion are

A

0.2 and .04

41
Q

A sample of 25 observations is taken from an infinite population. The sampling distribution of p is

A

approximately normal if np >_ 5 and n(1-P) >_ 5

42
Q

A sample of 51 observations will be taken from an infinite population. The population proportion equals 0.85. The probability that the sample proportion will be between 0.9115 and 0.946 is

A

0.0819

43
Q

Four hundred people were asked whether gun laws should be more stringent. Three hundred said “yes,” and 100 said “no.” The point estimate of the proportion in the population who will respond “yes” is

A

0.75

COMM 215 (11 decks)

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