In order to determine which is the probability for reading 4 books, you consider that the sum of all probabilities must be equal to 1.0. In that sense, you know that the unknow value of the probability distribution for x = 4 can be calculate as follow:
- Add up all known values of the probability distribution
0.23 + 0.27 + 0.18 + 0.07 = 0.75
- Next, you subtract the previous result to 1.0:
1.0 - 0.75 =0.25
The previous result is the value of the probability distribution for x = 4.
Hence, the probability of reading 4 books is 0.25, which is equivalent to 25.0%.
