4/5 is the right answer.....
You have to multiply by 16's and then divide the two numbers
121 is big enough to assume normality and not worry about the t distribution. By the 68-95-99.7 rule a 95% confidence interval includes plus or minus two standard deviations. So 95% of the cars will be in the mph range
The question is a bit vague, but it seems we're being asked for the 95% confidence interval on the average of 121 cars. The 121 is a hint of course.
The standard deviation of the average is in general the standard deviation of the individual samples divided by the square root of n:
So repeating our experiment of taking the average 121 cars over and over, we expect 95% of the averages to be in the mph range
That's probably the answer they're looking for.
Answer: Using the information of the conditional relative frequency table, 123 students in the survey said that math was their favorite subject.
Solution:
1. The survey was given to 120 male students.
Acconding with the table, the proportion of male students with Math as favorite subject is 0.35. The quantity of male students with Math as favorite subject would be:
0.35(120)=42 male students
2. The survey was given to 180 female students.
Acconding with the table, the proportion of female students with Math as favorite subject is 0.45. The quantity of female students with Math as favorite subject would be:
0.45(180)=81 female students
Then the total of students in the survey said that math was their favorite subject would be:
42 male students + 81 female students = 123 students
