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Suppose a tram arrives at regular intervals of 9 minutes. What is the probability density function [tex]\( f(t) \)[/tex] of the wait time at the station?

A. The probability density function is [tex]\( f(t) = \frac{7}{4} \)[/tex] on the interval [tex]\( 0 \leq t \leq 9 \)[/tex].

B. The probability density function is [tex]\( f(t) = \frac{1}{9} \)[/tex] on the interval [tex]\( 0 \leq t \leq 9 \)[/tex].


Sagot :

Your question seems to contain some typos and appears to be asking for the probability density function of waiting times at a station where a tram arrives at regular intervals of 9 minutes. Let's clarify and solve the problem step by step.

To find the probability density function of waiting times, here’s what we need to keep in mind:

1. Interval Details: The tram arrives every 9 minutes, so the waiting time for a tram is uniformly distributed between 0 and 9 minutes.

2. Uniform Distribution: For a uniform distribution over an interval, say [tex]\([a, b]\)[/tex], all outcomes are equally likely. The probability density function, [tex]\( f(x) \)[/tex], for a uniform distribution is given by:
[tex]\[ f(x) = \frac{1}{b - a} \text{ for } x \in [a, b] \][/tex]
[tex]\[ f(x) = 0 \text{ otherwise} \][/tex]

For our case:
- [tex]\( a = 0 \)[/tex]
- [tex]\( b = 9 \)[/tex]

So, the PDF [tex]\( f(x) \)[/tex] will be:
[tex]\[ f(x) = \frac{1}{9 - 0} = \frac{1}{9} \text{ for } x \in [0, 9] \][/tex]
[tex]\[ f(x) = 0 \text{ otherwise} \][/tex]

Given the provided options:
- The correct probability density function should be defined over the interval [tex]\( [0, 9] \)[/tex].

Assuming the options were:
A. [tex]\( f(\alpha) = \frac{7}{4} \)[/tex] on the interval [tex]\( 0 \leq \alpha \leq 2 \)[/tex].

B. [tex]\( f(x) = \frac{1}{4} \)[/tex] on the interval [tex]\( 0 \leq x \leq \infty \)[/tex].

Neither option is correctly describing the uniform distribution for waiting times between 0 and 9 minutes, given:

The correct PDF should be:
[tex]\[ f(x) = \frac{1}{9} \text{ for } 0 \leq x \leq 9 \][/tex]

So, let's propose the correct answer:
C. The probability density function is [tex]\( f(x) = \frac{1}{9} \)[/tex] on the interval [tex]\( 0 \leq x \leq 9 \)[/tex].