Several psychology students are unprepared for a surprise true/false test with 18 questions, and all of their answers are guesses. a. find the mean and standard deviation for the number of correct answers for such students. b. would it be unusual for a student to pass by guessing (which requires getting at least 15 correct answers)? why or why not?

26

step-by-step explanation:

a

step-by-step explanation:

see explanation

step-by-step explanation:

a

(6r + 7) + (13 + 7r) ( remove brackets and collect like terms )

= 6r + 7 + 13 + 7r

= 13r + 20

b

remove brackets and collect like terms

13 - r - 1 + r

= 12 - r

c

remove brackets and collect like terms

= - 8 - r + 2r - 4

= - 12 + r

d

remove brackets and collect like terms

= 7r - - - 6r

[-   - = - - = - ]

= r -

i’m sorry but i don’t know sorry