| Lifetime (in hours) | 0-20 | 20-40 | 40-60 | 60-80 | 80-100 | 100-120 |
| Frequency | 10 | 35 | 52 | 61 | 38 | 29 |
Determine the modal lifetimes of the components.
Solution:
From the given information the modular class is 60–80.
l = 60,
The frequencies are:
fm = 61, f1 = 52, f2 = 38 and h = 20
The equation to discover the mode is
\[Mode\text{ }=\text{ }l+\text{ }\left[ \left( fm-f1 \right)/\left( 2fm-f1-f2 \right) \right]\times h\]
Substitute the qualities in the equation, we get
\[\begin{array}{*{35}{l}}
Mode\text{ }=60+\left[ \left( 61-52 \right)/\left( 122-52-38 \right) \right]\times 20 \\
~ \\
Mode\text{ }=\text{ }60+\left( \left( 9\text{ }x\text{ }20 \right)/32 \right) \\
~ \\
Mode\text{ }=\text{ }60+\left( 45/8 \right)\text{ }=\text{ }60+\text{ }5.625 \\
\end{array}\] Along these lines, modular lifetime of the parts = 65.625 hours.