Question

Prepare a bivariate frequency distribution for the following data, taking class intervals for X as 35 – 45, 45 – 55, …. etc and for Y as 115 – 130, 130 – 145, … etc. where X denotes the age in years and Y denotes blood pressure for a group of 24 persons.
(55, 151) (36, 140) (72, 160) (38, 124) (65, 148) (46, 130) (58, 152) (50, 149) (38, 115) (42, 145) (41, 163) (47, 161) (69, 159) (60, 161) (58, 131) (57, 136) (43, 141) (52, 164) (59, 161) (44, 128) (35, 118) (62, 142) (67, 157) (70, 162)
Also, find Marginal frequency distribution of X.

Answer 1

Given X = Age in years
Y = Blood pressure
Bivariate frequency table can be prepared by taking class intervals 35 – 45, 45 – 55, …. etc for X and 115 – 130, 130 – 145, … etc for Y.
Bivariate frequency distribution is as follows:

Blood Pressure (y)/ Age in years(X)	35 – 45	45 – 55	55 –  65	65 – 75	Total (fy)
115 –  130	IIII (4)	–	–	–	4
130 –  145	II (2)	I (1)	III (3)	–	6
145 –  160	I (1)	I (1)	II (2)	III 3)	7
160 –  175	I (1)	II (2)	II (2)	II (2)	7
Total (fx)	8	4	7	5	24

Marginal frequency distribution of X:

X	35 – 45	45 – 55	55 –  65	65 – 75	Total
Frequency	8	4	7	5	24