1a. 20% of the young and 40% of the old breastfeed.

1b. 36% of the total breastfeed.

1c. A 1% smaple

Breast feed  Under 20    Greater than 20
       no      800          2400   3200
       yes     200          1600   1800
              1000          4000   5000

1d. Stratified sample

Breast feed      Under 20   Greater than 20
    No              800          600
    Yes             200          400
                   1000         1000

1e. Based on simple random sampling it will be 36%. Based on the stratified sample the estimate is 30%.

1f. The estimate will be 36%.

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2a. There will be variability among the clusters, but little variability within each one.

2b. I would try to design the clusters so that there is more variability within the clusters and less between them.

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