We are interested in the effect of smoking on births in the United States. Two v

Question

We are interested in the effect of smoking on births in the United States. Two variables or interest are the dependent variable, infant birth weight in ounces (bwght) and an explanatory variable, average number of cigarettes the mother smoked per day during pregnancy (cigs). The following simple regression was estimated using data on n = 1.388 births: bwght = 119.77 - 0.54 cigs What is the predicted birth weight when cigs = 0? What about when cigs = 20? Comment on the difference Does this simple regression necessarily capture a causal relationship between the child's birth weight and the mother's smoking habits? Explain. To predict a birth weight of 125 ounces, what would cigs have to be? Comment. The proposition of women in the sample who do not smoke while pregnant is about 0.85. Docs this help reconcile your findings from part (3)? What other factor can be related with the child's birth weight? Modify the simple regression as you guessed and make an additional assumption.

Explanation / Answer

1) given tha the regression equation is

B= 119.77- 0.54C , where B is birth weight and c is cigerrates

so when C = 0 , putting this in the above equation we get

B = 119.77 - 0.54*0 = 119.77,

now when the C = 20 , we get 119.77 - 0.54*20 = 108.97 , so there is a difference of 119.77-108.97 = 10.8 ounces

2) The regression equation tells us that for every unit change in the valeu of C , B changes by a factor of 0.54 , so every cigeratte that is consumed the birth weight decreases by 0.54 ounces . So yes , there apeears to be a negative relationship between the 2 variables , as cigerratte conssumption increases the the birth weight reduces

3) now again using the equation

B= 119.77- 0.54C and putting the value of B as 125 , we calculaet C as

125= 119.77- 0.54*C

C = -(125-119.77)/0.54= -9.68 , as the value of C cant be negative , we take the positive value as 9.68 , rounding it off to nearest integer , we get the value as 10 , or people should not smoke 10 cigerrates

4) the proportion who do not smoke is 0.85 , this means that for every 100 women 15 women do not smoke

Please note we can answer only 4 subparts as per the answering guidelines

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