Here is a data set ([tex]$n=117$[/tex]) that has been sorted:

[tex]\[
\begin{tabular}{|r|r|r|r|r|r|r|r|r|}
\hline
43 & 47.1 & 48.8 & 49.7 & 50.9 & 51.3 & 51.9 & 52.4 & 53.1 \\
\hline
53.1 & 53.4 & 53.6 & 53.8 & 53.8 & 53.8 & 54.8 & 55 & 55.6 \\
\hline
56.6 & 56.8 & 57.8 & 57.9 & 58 & 58.2 & 59.1 & 59.2 & 59.3 \\
\hline
59.4 & 59.9 & 59.9 & 60.2 & 60.8 & 60.8 & 61 & 61.1 & 61.5 \\
\hline
61.7 & 62.1 & 62.3 & 62.7 & 62.8 & 62.8 & 62.9 & 63 & 63 \\
\hline
63.4 & 63.5 & 63.5 & 63.6 & 63.9 & 64 & 64.1 & 64.2 & 64.2 \\
\hline
64.4 & 64.5 & 64.6 & 64.7 & 65 & 65 & 65.5 & 65.6 & 65.7 \\
\hline
65.8 & 66 & 66.5 & 66.7 & 67.1 & 67.6 & 67.6 & 67.6 & 67.7 \\
\hline
68 & 68.3 & 68.5 & 68.5 & 68.8 & 68.9 & 69 & 69.1 & 69.1 \\
\hline
69.1 & 69.5 & 69.6 & 69.7 & 70 & 70 & 70.1 & 70.6 & 70.7 \\
\hline
70.8 & 71.1 & 71.4 & 71.6 & 71.7 & 71.8 & 71.9 & 72.4 & 72.5 \\
\hline
72.9 & 73.6 & 73.9 & 74.7 & 74.9 & 75.2 & 75.4 & 76.1 & 76.3 \\
\hline
76.3 & 76.9 & 77 & 77.5 & 77.7 & 80.6 & 83.1 & 84 & 85.3 \\
\hline
\end{tabular}
\][/tex]

Find the 49th percentile.

Answer :

To find the 49th percentile of the given data set, we will follow these steps:

1. Determine the Position:
- With a given data set size of [tex]\( n = 117 \)[/tex], the percentile position can be calculated using the formula:
[tex]\[
\text{position} = \left(\frac{\text{percentile}}{100}\right) \times (n - 1)
\][/tex]
- Substituting the given values, we get:
[tex]\[
\text{position} = \left(\frac{49}{100}\right) \times (117 - 1) = 0.49 \times 116 = 56.84
\][/tex]

2. Locate the Necessary Indices:
- The decimal position, 56.84, indicates that the 49th percentile lies between the 56th and 57th values in the ordered data set.
- Note that indices start from zero, so these correspond to the 57th and 58th values in conventional counting.

3. Interpolation:
- Since the position is not a whole number, we need to interpolate between the values at the 56th (index 56) and 57th (index 57) positions.
- If the two calculated positions are 56 and 57, the values at these indices are 64.5 and 64.6, respectively.

4. Calculate the 49th Percentile Value:
- Determine the fractional part of the position, which is 0.84 (from 56.84).
- Use the formula for linear interpolation:
[tex]\[
\text{Value} = (1 - \text{fraction}) \times \text{Value}_{\text{lower}} + \text{fraction} \times \text{Value}_{\text{upper}}
\][/tex]
- Substituting the known values:
[tex]\[
\text{Value} = (1 - 0.84) \times 64.5 + 0.84 \times 64.6
\][/tex]
- Calculate:
[tex]\[
\text{Value} = 0.16 \times 64.5 + 0.84 \times 64.6 = 10.32 + 54.384 = 64.684
\][/tex]

Therefore, the 49th percentile of the data set is approximately 64.684.