In: Statistics and Probability
When studying radioactive material, a nuclear engineer found that over 365 days, 1,000,000 radioactive atoms decayed to 973,133 radioactive atoms, so 26,867 atoms decayed during 365 days.
a. Find the mean number of radioactive atoms that decayed in a day.
b. Find the probability that on a given day, 50 radioactive atoms decayed.
Thanks in advance!
SOLUTION:
From given data,
When studying radioactive material, a nuclear engineer found that over 365 days, 1,000,000 radioactive atoms decayed to 973,133 radioactive atoms, so 26,867 atoms decayed during 365 days.
Given that,
26,867 atoms decayed during 365 days
that is ,
P = Prob(decay per day)
=( 26867 / 1000000) * (1/365)
P =0.0000736
a. Find the mean number of radioactive atoms that decayed in a day
= n p
= 1000000 *0.0000736
= 73.6
74
b. Find the probability that on a given day, 50 radioactive atoms decayed.
X Normal ()
= 8.58
73.6
8.58
P[X= 50] = P[ 49.5 < X < 50.5 ]
= P[( 49.5 - ) / < Z < ( 50.5 - ) / ]
= P[( 49.5 - 73.6 ) / 8.58 < Z < ( 50.5 - 73.6 ) / 8.58 ]
= P[( 49.5 - 73.6 ) / 8.58 < Z < ( 50.5 - 73.6 ) / 8.58 ]
= P [ -2.81 < Z < -2.69]
= P(Z < -2.69) - P(Z < -2.81)
=0.0036 - 0.0025
= 0.0011