Questions: Refer to the accompanying data display that results from a sample of airport data speeds in Mbps. Complete parts (a) through (c) TInterval below.
Click the icon to view a t distribution table.
(13.046,22 15)
x=17.598
S x=16.01712719
n=50
a. What is the number of degrees of freedom that should be used for finding the critical value talpha / 2 ?
df=
(Type a whole number.)
Transcript text: Refer to the accompanying data display that results from a sample of airport data speeds in Mbps. Complete parts (a) through (c) TInterval below.
Click the icon to view a t distribution table.
(13.046,22 15)
\[
\begin{array}{l}
x=17.598 \\
S x=16.01712719 \\
n=50
\end{array}
\]
a. What is the number of degrees of freedom that should be used for finding the critical value $\mathrm{t}_{\alpha / 2}$ ?
\[
\mathrm{df}=
\]
(Type a whole number.)
Solution
Solution Steps
Step 1: Calculate Degrees of Freedom
To find the degrees of freedom (\(df\)) for the t-distribution, we use the formula:
\[
df = n - 1
\]
where \(n\) is the sample size. Given \(n = 50\):
\[
df = 50 - 1 = 49
\]
Step 2: Calculate the Confidence Interval
We calculate the confidence interval for the mean of a single population with unknown variance and a large sample size at a 95% confidence level using the formula:
\[
\bar{x} \pm t_{\alpha/2} \cdot \frac{s}{\sqrt{n}}
\]
where:
\(\bar{x} = 17.598\) (sample mean)
\(s = 16.01712719\) (sample standard deviation)
\(n = 50\) (sample size)
\(t_{\alpha/2} \approx 1.96\) for a 95% confidence level (from the t-distribution table for \(df = 49\))
Substituting the values into the formula:
\[
17.598 \pm 1.96 \cdot \frac{16.01712719}{\sqrt{50}}
\]
Calculating the margin of error:
\[
\text{Margin of Error} = 1.96 \cdot \frac{16.01712719}{\sqrt{50}} \approx 1.96 \cdot 2.264 = 4.44
\]
Thus, the confidence interval is:
\[
(17.598 - 4.44, 17.598 + 4.44) = (13.158, 22.038)
\]
Final Answer
The degrees of freedom is \( \boxed{49} \) and the confidence interval is \( \boxed{(13.16, 22.04)} \).