The National Vital Statistics Reports for November 2011 states that the U.S. pre

Question

The National Vital Statistics Reports for November 2011 states that the U.S. preterm birth rate for 2010 was about 12%. Preterm birth means premature birth. Is the percentage of preterm births lower this year?

Suppose that this year we select a random sample of 50 births. The conditions are not met for use of a normal model since the expected number of preterm births is only 6 (12% of 50). So we ran a simulation with p = 0.12.

Suppose that the sample of 50 babies has 4 that are preterm. This is 8% of the sample.

Do the data suggest that the percentage of preterm births in the U.S. is lower than 12% this year?

1. no because a 25.6% of the babies are preterm this year which is much higher than 12%

2 yes because only 8% are preterm this year which is lower than 12%

3. yes because sample proportions of .08 or less are unusual given the population proportion of .12

4. no because sample proportions of .08 or less are not unusual if the proportion of preterm births in the populationis .12

512 out of 2,000 random samples have a sample proportion of o.08 or lower. This is 25.6%, - 0.00 0.05 10 0.15 0.20 0.25 0.30 Sample proportions 4/50 = 0.08

Explanation / Answer

After resampling with population proportion 0.12 we find that the probability of sample proportion being less than or equal to 0.08 is 25.6 % which is more than 5% and hence it is not unusual to find sample proportion 0.08.

So, option 4 is correct

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