Answer:
0.0015 = 0.15% probability that if the motel books 150 guests, not enough seats will be available.
Step-by-step explanation:
Binomial probability distribution
Probability of exactly x successes on n repeated trials, with p probability.
Can be approximated to a normal distribution, using the expected value and the standard deviation.
The expected value of the binomial distribution is:
The standard deviation of the binomial distribution is:
Normal probability distribution
Problems of normally distributed distributions can be solved using the z-score formula.
In a set with mean and standard deviation
, the z-score of a measure X is given by:
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
When we are approximating a binomial distribution to a normal one, we have that ,
, if
and
.
150 guests booked:
This means that
85% of booked guests show up for their room.
This means that
Is the normal approximation suitable:
Both greater than 10, so yes.
Mean and standard deviation:
Find the probability that if the motel books 150 guests, not enough seats will be available.
More than 140 show up, which, using continuity correction, is , which is 1 subtracted by the p-value of Z when X = 140.5. So
has a p-value of 0.9985.
1 - 0.9985 = 0.0015.
0.0015 = 0.15% probability that if the motel books 150 guests, not enough seats will be available.