Question

Tattoos and Marriage

A study of tattoos on women and marriage found the following:

	Tattoo (T)	No Tattoo (T’)
Married (M)	200	800	1000
Not Married (M’)	300	400	700
	500	1200	1700

Compute these probabilities:  

(a) P (M and T)     

(b) P (M)     

(c) P (M/T)     

(d) P (M or T)  

(e) P (T/M)  

(f) Is there a relationship between marriage and having a tattoo?

Answer 1

Probability = total favourable outcomes / total number of possible outcomes

(a) P (M and T) = P(M T) = 200 / 1700 = 2/ 17

(b) P (M) = 1000 / 1700 = 10/ 17

(c) P (M/ T) = P(M T) / P(T) = (200/1700) / (500/1700)

  P (M/ T) = 200 /500 = 2/5

(d) P (M or T) = P ( M) + P(T) - P(M T)

P (M or T) = [1000/ 1700] + [ 500/ 1700] - [200/1700]

P (M or T) = 1300/ 1700 = 13/17

(e) P(T/M) = P(M T) / P(M) = (200/1700) / (1000/1700)

P(T/M) = 200/ 1000 = 1/5

(f) P(M/T) = 2/5 = .40 (P (M/T’) = 2/3 = .667 There is a relationship between having a tattoo and

marriage; those without a tattoo, are more likely to be married.