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For a point thrown in [0,3], how do you calculate the probability that its coordinate is less than 1?

This is a one-dimensional geometric probability problem. The sample space is the interval [0,3][0,3] with length 3. The event 'coordinate < 1' corresponds to the sub-interval [0,1)[0,1) with length 1. The probability is the ratio of lengths: 1/31/3.

Conditions

  • The point is uniformly distributed on [0,3][0,3].
  • The event is defined by the coordinate being less than 1.

Reasoning, step by step

  1. Identify the sample space Ω=[0,3]\Omega = [0,3] and its measure m(Ω)=3m(\Omega) = 3.
  2. Identify the event region A=[0,1)A = [0,1) and its measure m(A)=1m(A) = 1.
  3. Apply the formula P(A)=m(A)/m(Ω)P(A) = m(A)/m(\Omega).
  4. Calculate P(A)=1/3P(A) = 1/3.

Example

The script states: 'The qualifying points form [0,1)[0,1), whose length is 11. Dividing by the total length gives P(A)=1/3P(A)=1/3. The number line marks 0,1,2,30,1,2,3 to show these lengths.'

Common misconceptions

  • Including the endpoint 1 in the length calculation (measure is unaffected by single points).
  • Assuming discrete outcomes instead of continuous uniform distribution.
  • Calculating probability as 1/41/4 by counting integers 0,1,2,3.

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