3. In a survey of 447 women who had just given birth, the investigator recorded the lactation level of the women at different ages. You are provided with the summarized data, as given in Table 14.5, for help with the statistical issues below.

(a) The investigator wants to use a χ2 test to see whether age is associated with lactation level. Is it appropriate? Why? If not, what is your suggestion?

(b) Suppose that the investigator is interested in whether there is a difference in the lactation levels of the three age groups or between different age groups.

What is your analysis plan? What if the question is whether there is a difference in the lactation levels between women aged below and over 30 years?

(c) Suppose that the investigator presents you with the individual-level raw data regarding age and lactation amount (both as continuous data). Would there be any changes in the analysis plans for question (a)?