College

Listed in the accompanying table are waiting times (seconds) of observed cars at a Delaware inspection station. The data from two waiting lines are real observations, and the data from the single waiting line are modeled from those real observations. Assume that the two samples are independent simple random samples selected from normally distributed populations, and do not assume that the population standard deviations are equal. Complete parts (a) and (b).

a. Use a 0.01 significance level to test the claim that cars in two queues have different mean waiting times.

Let population 1 correspond to the single waiting line, and let population 2 correspond to the two waiting lines.

A. [tex]\( H_0: \mu_1 = \mu_2 \)[/tex]
[tex]\( H_1: \mu_1 \neq \mu_2 \)[/tex]

Calculate the test statistic.
[tex]\( t = 0.16 \)[/tex] (Round to two decimal places as needed.)

Find the [tex]\( P \)[/tex]-value.
[tex]\( P \)[/tex]-value [tex]\( = \square \)[/tex] (Round to three decimal places as needed.)

Waiting Times
[tex]\[
\begin{array}{|cc|cc|}
\hline
\multicolumn{2}{|c|}{\text{One Line}} & \multicolumn{2}{c|}{\text{Two Lines}} \\
\hline
63.6 & 733.6 & 63.5 & 865.4 \\
157.3 & 606.2 & 215.5 & 1089.8 \\
141.9 & 267.9 & 85.7 & 663.1 \\
278.5 & 310.2 & 339.9 & 518.2 \\
252.7 & 129.2 & 199.7 & 565.8 \\
476.3 & 133.2 & 630.3 & 267.9 \\
477.9 & 122.2 & 332.7 & 350.1 \\
473.6 & 128.8 & 328.6 & 94.8 \\
401.5 & 233.3 & 915.3 & 99.8 \\
721.6 & 460.7 & 552.6 & 162.6 \\
761.3 & 481.6 & 596.7 & 100.6 \\
692.3 & 518.1 & & \\
837.2 & 508.9 & & \\
902.7 & 579.9 & & \\
\hline
\end{array}
\][/tex]

Answer :

To test the claim that cars in two queues (one line versus two lines) have different average waiting times, we need to perform a hypothesis test using a two-sample t-test. Here’s a step-by-step solution:

### Step 1: Formulate the Hypotheses

- Null Hypothesis ([tex]\(H_0\)[/tex]): The means of the waiting times for the two populations (one line and two lines) are equal. Mathematically, [tex]\( \mu_1 = \mu_2 \)[/tex].
- Alternative Hypothesis ([tex]\(H_1\)[/tex]): The means of the waiting times for the two populations are not equal. Mathematically, [tex]\( \mu_1 \neq \mu_2 \)[/tex].

### Step 2: Determine the Significance Level

We are using a significance level of 0.01.

### Step 3: Calculate the Test Statistic

The test statistic for comparing two means is calculated using the formula for an independent two-sample t-test. However, the values are not computed manually in this explanation.

The computed value for the test statistic is [tex]\( t = 0.16 \)[/tex].

### Step 4: Determine the Degrees of Freedom

When using a two-sample t-test with unequal variances, we use the Welch-Satterthwaite equation to estimate the degrees of freedom. This formula isn't explicitly calculated here, but it accounts for the sample sizes and variances.

### Step 5: Calculate the p-value

The p-value is calculated using the test statistic and the degrees of freedom. For a two-tailed test, we compare the absolute value of the test statistic to a t-distribution.

The resulting p-value is [tex]\( \text{P-value} = 0.874 \)[/tex].

### Step 6: Conclusion

Compare the p-value to the significance level:

- If the p-value is less than the significance level (0.01), we reject the null hypothesis.
- If the p-value is greater than the significance level, we fail to reject the null hypothesis.

Since [tex]\( 0.874 > 0.01 \)[/tex], we fail to reject the null hypothesis. This means there is not enough evidence to conclude that the average waiting times for the two queues are different at the 0.01 significance level.

Therefore, based on the data, we cannot claim there is a significant difference in the average waiting times between the one line and two lines at the Delaware inspection station.

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