According to a study, 33% of college students call their families each week. A social scientist, who studies communication, would like to study communication between college students and their family members. If the social scientist selects 60 college students, use a calculator to find the probability that of those 60 college students, between 18 and 20 of them call their families weekly. Round your answers to two decimal places.

31.49% probability that of those 60 college students, between 18 and 20 of them call their families weekly.

Step-by-step explanation:

For each student, there are only two possible outcomes. Either they call their families each week, or they do not. The probability of a student calling their family each week is independent of other students. So we use the binomial probability distribution to solve this question.

Binomial probability distribution

The binomial probability is the probability of exactly x successes on n repeated trials, and X can only have two outcomes.

In which is the number of different combinations of x objects from a set of n elements, given by the following formula.

And p is the probability of X happening.

33% of college students call their families each week.

This means that

60 college students

This means that

Probability that of those 60 college students, between 18 and 20 of them call their families weekly.

31.49% probability that of those 60 college students, between 18 and 20 of them call their families weekly.

there is no

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional