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A survey of 2,250 adults reported that 59% watch news videos. Complete parts (a) through (c) below.

a. Suppose that you take a sample of 100 adults. If the population proportion of adults who watch news videos is 0.59, what is the probability that fewer than half in your sample will watch news videos? Round to four decimal places as needed.

b. Suppose that you take a sample of 500 adults. If the population proportion of adults who watch news videos is 0.59, what is the probability that fewer than half in your sample will watch news videos? Round to four decimal places as needed.

c. Discuss the effect of sample size on the sampling distribution of the proportion in general and the effect on the probabilities in parts (a) and (b). Choose the correct answer below.

Answer :

a) The probability that fewer than half people in a sample of 100 adults will watch news videos is approximately 0.0338.

b) The probability that fewer than half people in a sample of 500 adults will watch news videos is nearly 0 and so for practical purposes is considered to be 0.

c) The correct answer is:

B. Increasing the sample size by a factor of 5 decreases the standard error by a factor of √5. This causes the sampling distribution of the proportion to become more concentrated around the true population proportion of 0.59 and decreases the probability in part​ (b).

To find the probability of fewer than half in the sample watching news videos, we can use the normal approximation to the binomial distribution since the sample size is sufficiently large.

Given information are:

Population proportion of adults who watch news videos (p) = 0.59

For part a), sample size (n) = 100

and for part b), sample size (n) = 500

Now,

For part (a), we have, n = 100

Mean (μ) = np = 100 × 0.59 = 59

Standard deviation (σ) = [tex]\sqrt{np(1-p)} = \sqrt{100 \times 0.59 \times 0.41}[/tex] ≈ 4.918

We need to find the probability of fewer than 50 adults watching news videos, which is equivalent to finding the probability of getting less than 50 successes in a binomial distribution with parameters n = 100 and p = 0.59.

Using the normal approximation, we standardize the value as:

[tex]z = \frac{x - \mu}{\sigma}[/tex]

where x = 50, μ = 59, and σ = 4.918

Thus the z-score is,

[tex]z = \frac{50 - 59}{4.918}[/tex] ≈ -1.83001

Using a standard normal distribution table or calculator, the probability corresponding to z ≈ -1.83001 is approximately 0.0338.

For part (b), we have n = 500

Mean (μ) = np = 500 × 0.59 = 295

Standard deviation (σ) = [tex]\sqrt{np(1-p)} = \sqrt{500 \times 0.59 \times 0.41}[/tex] ≈ 10.9977

We need to find the probability of fewer than 250 adults watching news videos, which is equivalent to finding the probability of getting less than 250 successes in a binomial distribution with parameters n = 500 and p = 0.59.

Using the normal approximation, we standardize the value:

[tex]z = \frac{x - \mu}{\sigma}[/tex]

where x = 250, μ = 295, and σ = 10.9977

Thus the z-score is,

[tex]z = \frac{250 - 295}{10.9977}[/tex] ≈ -4.0918

The probability corresponding to z ≈ -4.0918 is extremely close to 0, as this value corresponds to an extremely low tail area in the standard normal distribution. It can be considered practically 0 for most practical purposes.

Now, as the sample size increases, the sampling distribution of the proportion becomes more normal-shaped due to the central limit theorem. With a larger sample size, the standard deviation of the sampling distribution decreases, leading to a narrower distribution.

Thus, in general, as the sample size increases, the probabilities in parts (a) and (b) become more accurate and reliable, as the normal approximation to the binomial distribution becomes more appropriate with larger sample sizes.

Question:

A survey of 2,250 adults reported that 59% watch news videos. Complete parts (a) through (c) below.

a. Suppose that you take a sample of 100 adults. If the population proportion of adults who watch news videos is 0.59, what is the probability that fewer than half in your sample will watch news videos? Round to four decimal places as needed.

b. Suppose that you take a sample of 500 adults. If the population proportion of adults who watch news videos is 0.59, what is the probability that fewer than half in your sample will watch news videos? Round to four decimal places as needed.

c. Discuss the effect of sample size on the sampling distribution of the proportion in general and the effect on the probabilities in parts (a) and (b). Choose the correct answer below.

A. Increasing the sample size by a factor of 5 increases the standard error by a factor of √5. This causes the sampling distribution of the proportion to become more concentrated around the true population proportion of 0.59 and increases the probability in part​ (b).

B. Increasing the sample size by a factor of 5 decreases the standard error by a factor of √5. This causes the sampling distribution of the proportion to become more concentrated around the true population proportion of 0.59 and decreases the probability in part​ (b).

C. The probabilities in parts​ (a) and​ (b) are the same. Increasing the sample size does not change the sampling distribution of the proportion.

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