Your alarm clock is broken and always rings with a delay. For example, last night, you set your alarm for 7:30 AM but your alarm rang at 7:42 AM. However, the delay is not constant. After much data collection, you realize that the alarm clock’s delay time (in minutes) can be reasonably modeled as a continuous random variable T with pdf f(t)=ce^(-t/15) for t>=0 and f(t)=0 otherwise. Answer the following questions: (a) What is the value of c? (b) What is the mean delay? (c) What is the variance in the delay? (d) If you wanted your alarm to ring at 7:30 AM, approximately what time should you set your alarm so that 95% of the time, the alarm rings before 7:30 AM?

Bayobusalue

Bayobusalue

Answered question

2022-11-12

Your alarm clock is broken and always rings with a delay. For example, last night, you set your alarm for 7:30 AM but your alarm rang at 7:42 AM. However, the delay is not constant. After much data collection, you realize that the alarm clock’s delay time (in minutes) can be reasonably modeled as a continuous random variable T with f ( t ) = c e t / 15  for  t 0  and  f ( t ) = 0 otherwise.
Answer the following questions:
(a) What is the value of c?
(b) What is the mean delay?
(c) What is the variance in the delay?
(d) If you wanted your alarm to ring at 7:30 AM, approximately what time should you set your alarm so that 95% of the time, the alarm rings before 7:30 AM?

Answer & Explanation

fonfonvkdpf

fonfonvkdpf

Beginner2022-11-13Added 13 answers

Solution :
Part a
Here we have,
f ( t ) = c e t 15 ; t 0
Therefore we have,
0 f ( t ) d t = c × 15 = 1 c = 1 15
This is the required value of ‘c’.
Part b
The mean is given by,
E [ T ] = 0 t 15 e t 15 d t = 15
Part c
The second moment is given by,
E [ T 2 ] = 15 2 + 15
σ T 2 = 15 2 + 15 15 2 = 15

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