问题


There is a single choice question about high school statistics. Answer the question by replying A, B, C or D.
Question: A farmer wants to know whether a new fertilizer has increased the mean weight of his apples. With the old fertilizer, the mean weight was 4.0 ounces per apple. The farmer decides to test H0: μ = 4.0 ounces versus Ha : μ > 4.0 ounces, at a 5 percent level of significance, where μ = the mean weight of apples using the new fertilizer. The weights of apples are approximately normally distributed. The farmer takes a random sample of 16 apples and computes a mean of 4.3 ounces and a standard deviation of 0.6 ounces. Which of the following gives the p-value for this test?
A. P(Z > 2)
B. P(Z < 2)
C. P(t > 2) with 15 degrees of freedom
D. P(t < 2) with 15 degrees of freedom
Answer:

答案

模型 模型答案 正确答案
金声玉亮2.0

C. P(t > 2) with 15 degrees of freedom

Explanation:

Since the sample size is small (n = 16), we use the t-distribution instead of the standard normal distribution (Z). The degrees of freedom for the t-distribution is n - 1 = 16 - 1 = 15.

The test is a one-tailed test (Ha: μ > 4.0), so we are interested in the area to the right of the test statistic. The test statistic is calculated as:

t = (x̄ - μ) / (s / √n)
= (4.3 - 4.0) / (0.6 / √16)
= 2

So, the p-value is the probability of observing a t-statistic greater than 2, with 15 degrees of freedom, which is P(t > 2) with 15 degrees of freedom.
C
deepseekr1

The farmer uses a t-test because the population standard deviation is unknown and the sample size is small (n=16). The test statistic is calculated as \( t = \frac{4.3 - 4.0}{0.6/\sqrt{16}} = 2 \). With 15 degrees of freedom (n-1) and a right-tailed alternative hypothesis (Ha: μ > 4.0), the p-value is the probability \( P(t > 2) \) with 15 degrees of freedom.

**Answer:** C. P(t > 2) with 15 degrees of freedom
C
gpto1 To determine the p-value for this test, we need to follow these steps:

1. **Identify that the population standard deviation is unknown** and the sample size is small (\( n = 16 \)), so we should use the **t-test**.

2. **Calculate the test statistic using the t-distribution:**

\[
t = \frac{\bar{x} - \mu_0}{s / \sqrt{n}}
\]

Where:
- \( \bar{x} = 4.3 \) ounces (sample mean)
- \( \mu_0 = 4.0 \) ounces (hypothesized population mean)
- \( s = 0.6 \) ounces (sample standard deviation)
- \( n = 16 \) (sample size)

Plugging in the values:

\[
t = \frac{4.3 - 4.0}{0.6 / \sqrt{16}} = \frac{0.3}{0.6 / 4} = \frac{0.3}{0.15} = 2
\]

3. **Determine the degrees of freedom (df):**

\[
\text{df} = n - 1 = 16 - 1 = 15
\]

4. **Since the alternative hypothesis is \( H_a: \mu > 4.0 \) ounces**, this is a **right-tailed test**.

5. **Express the p-value:**

The p-value is the probability of observing a test statistic as extreme as, or more extreme than, the calculated value under the null hypothesis. For a right-tailed t-test:

\[
\text{p-value} = P(t > 2) \text{ with } 15 \text{ degrees of freedom}
\]

**Therefore, the correct answer is:**

**C. P(t > 2) with 15 degrees of freedom**
C
GPT-4o To determine the p-value for this test, we need to perform a one-sample t-test since the sample size is small (n = 16) and the population standard deviation is unknown. Let's calculate the test statistic first.

The test statistic for a one-sample t-test is given by:
\[ t = \frac{\bar{x} - \mu_0}{s / \sqrt{n}} \]
where:
- \(\bar{x}\) is the sample mean (4.3 ounces),
- \(\mu_0\) is the population mean under the null hypothesis (4.0 ounces),
- \(s\) is the sample standard deviation (0.6 ounces), and
- \(n\) is the sample size (16).

Plugging in the values:
\[ t = \frac{4.3 - 4.0}{0.6 / \sqrt{16}} = \frac{0.3}{0.15} = 2 \]

Now, we need to find the p-value for this t-test with 15 degrees of freedom (since \( df = n - 1 = 16 - 1 = 15 \)).

The p-value for this test is \(P(t > 2)\) with 15 degrees of freedom.

So, the correct answer is:
C. P(t > 2) with 15 degrees of freedom
C
llama3.1-70B-Instruct

A
C
llama3.1-405B-Instruct

C. The population standard deviation is unknown, so the t -distribution must be used. The degrees of freedom for the t -distribution are n – 1 = 16 – 1 = 15. The alternative hypothesis is one-sided, so the p -value is the area to the right of t = 2. This is (C). (A) and (B) are incorrect because they use the z -distribution. (D) is incorrect because it is the area to the left of t = 2.
The best answer is C.
C
DeepSeek-Coder-V2 C. P(t > 2) with 15 degrees of freedom C
Qwen2-72B-Instruct C. P(t > 2) with 15 degrees of freedom C
baichuan4 C C
doubao C

The sample size is 16, so the degrees of freedom is 16 - 1 = 15. We use the t-distribution since the population standard deviation is unknown. The test statistic t = (4.3 - 4.0)/(0.6/√16) = 2. So we need to find P(t > 2) with 15 degrees of freedom.
C
minimax To find the p-value for this test, we need to calculate the test statistic and then compare it to the critical value from the standard normal distribution (Z-distribution) because the sample size is large enough (n = 16) for the Central Limit Theorem to apply.

The test statistic is calculated using the formula:

\[ Z = \frac{\bar{x} - \mu_0}{\frac{\sigma}{\sqrt{n}}} \]

Where:
- \(\bar{x}\) is the sample mean (4.3 ounces)
- \(\mu_0\) is the hypothesized population mean under the null hypothesis (4.0 ounces)
- \(\sigma\) is the sample standard deviation (0.6 ounces)
- \(n\) is the sample size (16)

Plugging in the values:

\[ Z = \frac{4.3 - 4.0}{\frac{0.6}{\sqrt{16}}} \]
\[ Z = \frac{0.3}{\frac{0.6}{4}} \]
\[ Z = \frac{0.3}{0.15} \]
\[ Z = 2 \]

Now we need to find the p-value associated with this Z-value. Since we are conducting a one-tailed test (Ha: μ > 4.0 ounces), we are interested in the probability that Z is greater than 2.

The correct answer is:
A. P(Z > 2)
C
kimi To find the p-value for this test, we need to calculate the test statistic and then find the corresponding p-value.

Given:
- Null hypothesis (H0): μ = 4.0 ounces
- Alternative hypothesis (Ha): μ > 4.0 ounces
- Sample mean (x̄): 4.3 ounces
- Population mean (μ₀): 4.0 ounces
- Sample standard deviation (s): 0.6 ounces
- Sample size (n): 16

The test statistic for a one-sample t-test is calculated as follows:

t = (x̄ - μ₀) / (s / √n)

Plugging in the values:

t = (4.3 - 4.0) / (0.6 / √16)
t = 0.3 / (0.6 / 4)
t = 0.3 / 0.15
t = 2

Since we are testing for an increase in the mean weight (μ > 4.0), we are interested in the right-tailed test, which means we want to find the probability that the test statistic is greater than 2.

Therefore, the correct answer is:

A. P(Z > 2)

However, it's important to note that this is a one-sample t-test, and the test statistic should be compared to a t-distribution with n-1 degrees of freedom (15 in this case), not a Z-distribution. But since the question is asking for the p-value corresponding to the test statistic, and the test statistic is 2, the correct interpretation of the p-value is the probability that a t-distribution with 15 degrees of freedom exceeds 2. So, the closest answer to the p-value would be:

C. P(t > 2) with 15 degrees of freedom

But this is not the standard way to express the p-value for a right-tailed test. The standard way would be to find P(t > 2) for the t-distribution with 15 degrees of freedom, which is the area to the right of 2 on the t-distribution curve. The p-value is typically the area to the right of the test statistic in a right-tailed test, or the area to the left in a left-tailed test. Since the question does not provide a standard way to express the p-value for a t-test, we have to choose the closest answer, which is option C.
C
wenxinyiyan A C
zhipu To determine the p-value for the farmer's test, we need to use the appropriate statistical test since the sample size is small (n = 16) and the population standard deviation is unknown. Therefore, we use the t-distribution.

The test statistic \( t \) can be calculated using the formula:
\[ t = \frac{\bar{x} - \mu_0}{s / \sqrt{n}} \]

Where:
- \(\bar{x}\) is the sample mean (4.3 ounces)
- \(\mu_0\) is the hypothesized population mean (4.0 ounces)
- \(s\) is the sample standard deviation (0.6 ounces)
- \(n\) is the sample size (16)

Plugging in the values:
\[ t = \frac{4.3 - 4.0}{0.6 / \sqrt{16}} = \frac{0.3}{0.15} = 2 \]

Since the alternative hypothesis \( Ha \) is \( \mu > 4.0 \), we are looking for the probability that the t-statistic is greater than 2 with \( n - 1 = 16 - 1 = 15 \) degrees of freedom.

Thus, the correct p-value is given by \( P(t > 2) \) with 15 degrees of freedom.

The correct answer is:
C. \( P(t > 2) \) with 15 degrees of freedom
C
gpto1 To determine the p-value for this test, we need to follow these steps:

1. **Identify that the population standard deviation is unknown** and the sample size is small (\( n = 16 \)), so we should use the **t-test**.

2. **Calculate the test statistic using the t-distribution:**

\[
t = \frac{\bar{x} - \mu_0}{s / \sqrt{n}}
\]

Where:
- \( \bar{x} = 4.3 \) ounces (sample mean)
- \( \mu_0 = 4.0 \) ounces (hypothesized population mean)
- \( s = 0.6 \) ounces (sample standard deviation)
- \( n = 16 \) (sample size)

Plugging in the values:

\[
t = \frac{4.3 - 4.0}{0.6 / \sqrt{16}} = \frac{0.3}{0.6 / 4} = \frac{0.3}{0.15} = 2
\]

3. **Determine the degrees of freedom (df):**

\[
\text{df} = n - 1 = 16 - 1 = 15
\]

4. **Since the alternative hypothesis is \( H_a: \mu > 4.0 \) ounces**, this is a **right-tailed test**.

5. **Express the p-value:**

The p-value is the probability of observing a test statistic as extreme as, or more extreme than, the calculated value under the null hypothesis. For a right-tailed t-test:

\[
\text{p-value} = P(t > 2) \text{ with } 15 \text{ degrees of freedom}
\]

**Therefore, the correct answer is:**

**C. P(t > 2) with 15 degrees of freedom**
C
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