Questions: Find the sample standard deviation for the following Grouped Frequency Data Table (GFDT).
Lower Class Limit Upper Class Limit Frequency
---------
70 74 5
75 79 7
80 84 4
85 89 4
90 94 7
95 99 10
100 104 15
105 109 9
110 114 4
Transcript text: Find the sample standard deviation for the following Grouped Frequency Data Table (GFDT).
\begin{tabular}{|l|l|l||}
\hline \begin{tabular}{l}
Lower Class \\
Limit
\end{tabular} & \begin{tabular}{l}
Upper Class \\
Limit
\end{tabular} & Frequency \\
\hline 70 & 74 & 5 \\
\hline 75 & 79 & 7 \\
\hline \hline 80 & 84 & 4 \\
\hline 85 & 89 & 4 \\
\hline 90 & 94 & 7 \\
\hline 95 & 99 & 10 \\
\hline 100 & 104 & 15 \\
\hline 105 & 109 & 9 \\
\hline 110 & 114 & 4 \\
\hline \hline
\end{tabular}
Solution
Solution Steps
Step 1: Calculate the Mean
The mean \( \mu \) of the dataset is calculated using the formula:
\[
\mu = \frac{\sum x_i}{n}
\]
where \( \sum x_i = 6130.0 \) and \( n = 65 \). Thus,
\[
\mu = \frac{6130.0}{65} = 94.31
\]
Step 2: Calculate the Variance
The variance \( \sigma^2 \) is calculated using the formula:
\[
\sigma^2 = \frac{\sum (x_i - \mu)^2}{n-1}
\]
Given that \( \sigma^2 = 142.25 \), we can state:
\[
\sigma^2 = 142.25
\]
Step 3: Calculate the Standard Deviation
The standard deviation \( \sigma \) is the square root of the variance:
\[
\sigma = \sqrt{142.25} = 11.93
\]
Final Answer
The variance and standard deviation of the dataset are: