Question 2
The following data gives the information on the observed lifetimes (in hours) of 225 electrical components:
Lifetimes(in hours)0−2020−4040−6060−8080−100100−120Frequency103552613829
Determine the modal lifetimes of the components.
From the data given above, we observe that maximum class frequency is 61 of class interval 60 - 80.
So, modal class = 60 - 80
Lower class limit l of modal class = 60
Frequency (f1) of modal class = 61
Frequency (f0) of class preceding the modal class = 52
Frequency (f2) of class succeeding the modal class = 38
Class size h = 20
Mode=l+(f1−f02f1−f0−f2)×h=60+(61−522(61)−52−38)(20)=60+(9122−90)(20)=60+(9×2032)=60+9016=60+5.625=65.625
So, modal lifetime of electrical components is 65.625 hours.