The ratio of Bulls to Bears shirts in a sporting goods store is 4 : 7. If there are 33 shirts altogether, how many Bulls shirts
2 answers:
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Answer:
probability that all the 15 students selected are girls
Step-by-step explanation:
The selection is from a sample without replacement, so we use the hypergeometric distribution to solve this question.
Hypergeometric distribution:
The probability of x sucesses is given by the following formula:
In which:
x is the number of sucesses.
N is the size of the population.
n is the size of the sample.
k is the total number of desired outcomes.
Combinations formula:
is the number of different combinations of x objects from a set of n elements, given by the following formula.
All girls from the first group:
20 students, so
10 girls, so
5 students will be selected, so
We want all of them to be girls, so we find P(X = 5).
All girls from the second group:
20 students, so
5 girls, so
5 students will be selected, so
We want all of them to be girls, so we find P(X = 5).
All girls from the third group:
20 students, so
8 girls, so
5 students will be selected, so
We want all of them to be girls, so we find P(X = 5).
All 15 students are girls:
Groups are independent, so we multiply the probabilities:
probability that all the 15 students selected are girls