In a study of behavioral asymmetries, 2,391 women were asked which hand they pre
ID: 3205410 • Letter: I
Question
In a study of behavioral asymmetries, 2,391 women were asked which hand they preferred to use (e.g., to write) and which foot they preferred to use (for instance, to kick a ball). The results are reported in the table
(a) Estimate the conditional probability that a woman is right-footed, given that she is right-handed.
(b) Estimate the conditional probability that a woman is right-footed, given that she is left-handed.
(c) Test the null hypothesis that hand preference and foot preference are independent.
Preferred Hand Preferred Foot Right Right 2012 Right Left 142 Left Right 121 Left Left 116 Total 2391Explanation / Answer
a) total right haded women =2012+142=2154
hence conditional probability that a woman is right-footed, given that she is right-handed =2012/2154=0.9341
b)) total left haded women=121+116 =237
hence conditional probability that a woman is right-footed, given that she is left-handed =121/237=0.5105
c)if hand preference and foot preference are independent then
conditional probability that a woman is right-footed, given that she is right-handed should equal to probabilty of a women to be right footed
total right footed women =2012+121=2133
probabilty of right footed women =2133/2391 =0.8921
which is not equal to conditional probability that a woman is right-footed, given that she is right-handed,
hence reject the null hypothesis.