Professor Lara is sometimes a very cranky professor and appa

Professor Lara is sometimes a very cranky professor and apparently her crankiness is random. Fearing this, you observe her for 22 days (total probability) and she is cranky for 9 of those days.

a) What is the probability that she will be cranky today?

b) What is the probability that she will not be cranky today?

c) What is the probability she will be cranky this Wednesday and next

Wednesday?

d) What is the probability she will not be cranky this Wednesday but will

cranky next Wednesday?

e) What is the probability she will be cranky today or tomorrow?

Solution

(a)The probability that she will be cranky today is: 9/22=0.4

(b)The probability that she will not be cranky today is: 1-0.4=0.6

(c)The probability she will be cranky this Wednesday and next

Wednesday: 0.4*0.4=0.16 (Both the events are independent)

(d)The probability she will not be cranky this Wednesday but will

cranky next Wednesday: 0.4*0.6=0.24