A teacher chooses 4 different students to answer questions. There are 21 sophomores and 8 freshmen. Find the probability of the teacher choosing 2 sophomores, then 2 freshmen.

There are C(29, 4) = 29!/(4! (29 - 4)!) ways of selecting any 4 students from the total 21 + 8 = 29 students.

The teacher has C(21, 2) = 21!/(2! (21 - 2)!) ways of picking out 2 sophomores and C(8, 2) = 8!/(2! (8 - 2)!) ways of picking out 2 freshmen, so there are

C(21, 2) • C(8, 2) = 5880

possible ways of picking out 2 sophomore and 2 freshmen.

The probability of picking out a group of students like this is then

C(21, 2) • C(8, 2) / C(29, 4) = 280/1131 ≈ 0.2476

the answer to the question is punishment. or more specifically, positive punishment.

positive punishment occurs when a behavior is given a negative consequence for the individual doing the behavior.

sara no longer wants to ask questions (the behavior) because she is ridiculed by mr. smith (the punishment).

reinforcement is inaccurate because reinforcement always gives positive consequences for the individual doing the behavior, be it by introducing a pleasant consequence or removing an unpleasant one.

answer:

for this and for the points

explanation: