Hurry !

the performing arts teacher wants to know whether the students in the entire school prefer music or theater.

the teacher draws a random sample from the following groups:

all school teachers
all students in the band
all boys in each grade
all students in each grade

which of the following groups best represents the population she should take a random sample from to get the best results for her survey?

all school teachers
all students in the band
all boys in each grade
all students in each grade

stanley wants to know how many students in his school enjoy watching talk shows on tv. he asks this question to all 24 students in his history class and finds that 55% of his classmates enjoy watching talk shows on tv. he claims that 55% of the school's student population would be expected to enjoy watching talk shows on tv.

is stanley making a valid inference about his population?

no, it is not a valid inference because he asked all 24 students in his history class instead of taking a sample from his math class
no, it is not a valid inference because his classmates do not make up a random sample of the students in the school
yes, it is a valid inference because his classmates make up a random sample of the students in the school
yes, it is a valid inference because he asked all 24 students in his history class

a researcher posts an online advertisement offering $25 in exchange for participation in a short study. the researcher accepts the first 10 people who respond to the advertisement.

which of the following statements is true about the sample?

it is not a valid sample because it is only a short study.
it is a valid sample because money was offered to participants.
it is a valid sample because the first 10 people were selected to participate.
it is not a valid sample because it is not a random sample of the population.