Math Is Fun Forum

Hi this is Bobs again I was wondering if you could check statistics for me! I have asked so many questions thanks for your help! it is jsut that stats is a difficult subject for me!

Data was collected outside a popular new restaurant to determine the mean waiting time to be seated at a table. Assume the data was normally distributed with a mean of 45 min and standard deviation of 12 min
determine the probability that a randomly selected person has to wait less than 20 min
So for this questionI would use:
normalcdf(0,20,45,12)
= 0.0185219157

on to part B

determine the probability that a randomly selected person has to wait more than 1 h?
they have to wait more than an hour
so I cant use the normalCDF thing

thanks once again!

A committee is to be formed investigates what activities teenagers have available in small communities. The committee is to have 7, chosen randomly from interested community member. There are 10 parents, 5 teenagers, and 4 adults without children who have all expressed an interest in serving on the committee. What is the probability that the adults without children are all on the committee?

7 members
4 adults
19 people all together
7P4 = 840
19P4= 93024
7P4 /19P4
= .009--> 1%

Statistics Canada reported that approximately 76% of families in Edmonton consist of married couples. There are 22 students in grade 3.  what is the probability that exactly half of the students have families where the parents are defined as married couples?    What is the probability that at least one student does not have parents that are defined as married couples?

Number of trials: 22
Probability: 0.76
K= 11, 12, 13, 14, 15, 16…….. 23
Sum (binompdf (22, 0.76{11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22})
= 0.998
Or  do I do it this way:
I did it this way:
Number of trials: 22
Probability: 0.76
K= 1,2,3,4,5,6,7,8,9,10 11, 12, 13, 14, 15, 16…….. 23
Sum (binompdf (22, 0.76{ 1,2,3,4,5,6,7,8,9,10,11, 12, 13, 14, 15, 16, 17,
18, 19, 20, 21, 22})
= 1