Question

You believe that the two most important variables that influence a healthy baby’s birth weight are the mother’s annual household income (under $50,000, $50,000-$100,000, $100,000-$250,000, or over $250,000) and the mother’s primary diet (Mediterranean, vegetarian, or Atkins). You randomly select 30 pregnant women from each of the different income brackets and randomly assign each group of 30 to the different diet groups (10 in each group). After strictly following their assigned diet throughout their pregnancy, the mothers’ babies are weighed at birth. (If any of the babies are born prematurely or are otherwise unhealthy, they are excluded from this study.)

(a) Identify the response variable and the two factors. What are the levels of the factors? How many treatments are there?

(b) Is this an observational study, a designed study, or some combination of both? Explain

Answer 1

a)

response variable is birth weight

two factors are

i) household income (level - (under $50,000, $50,000-$100,000, $100,000-$250,000, or over $250,000) }

ii) mother’s primary diet - {level - (Mediterranean, vegetarian, or Atkins)}

b)

This is combination of both as

primary diet was assigned as treatment

whereas you choose difference sample in household income