Question

The following data have to do with the relationship between maternal smoking (# of cigarettes smoked per day,

which is variable X) and infant birth weight (which is variable Y). (∑X, ∑X², ∑Y, ∑Y², and ∑XY have already been

calculated for you and are shown below in red font.)

Cigarettes Per Day (X) X²    Infant Birth Weight (Y) Y² XY

2                                                        4                                            7.5                                 56.25                             15.0

6                                                      36                                            7.2                                 51.84                             43.2

10                                                100                                            6.9                                 47.61                             69.0

12                                                  144                                            6.2                                 38.44                             74.4

14                                                196    5.8 33.64 81.2

∑X = 44                                        ∑X² = 480                              ∑Y = 33.6                      ∑Y² = 227.78             ∑XY = 282.8

What is the y-intercept (a) for this data?

		6.05
		6.67
		7.95
		8.33
		57.90
		5.49

Answer 1

Solution:

Given:

Number of cigarettes smoked per day which is variable X and infant birth weight which is variable Y.

We are given following totals:

n = number of pairs = 5

We have to find y-intercept (a).

It is given by:

where

and

Thus

Now find:

Thus y-intercept is:

Closest option from given options is: 7.95

Thus correct choice is : 7.95