Posted by **Ashley** on Thursday, June 30, 2011 at 2:13pm.

The proportion of baby boys born in the United States has historically been 0.512. You choose an SRS of 55 newborn babies and find that 47% are boys. Do ALL calculations to 5 decimal places before rounding.

(d) In a random sample of 55 newborn babies, what is the probability that 47% of the sample are boys. (Use 3 decimal places). Hint: you are asked to find P( < .47 ). To calculate this first find the z-score and then look up the answer in the Z table.

- statistics -
**MathGuru**, Thursday, June 30, 2011 at 5:40pm
Formula for z-score:

z = (x - mean)/sd

Find mean:

mean = np = (55)(0.512) = ?

Find standard deviation:

sd = √npq = √(55)(0.512)(0.488) = ?

Note: q = 1 - p

Finish both calculations.

Substitute mean and standard deviation into the z-formula. Use 25.85 for x (0.47 * 55 = 25.85).

Once you have the z-score, use the z-table to determine your probability.

I hope this will help get you started.

- statistics -
**Ashley**, Thursday, June 30, 2011 at 8:32pm
Thank you sooo much!! Also thanks for posting steps and not just an answer.

## Answer this Question

## Related Questions

- statistics - the wieights of newborn babies are distributed normally, with the ...
- statistics - the weights of newborn babies are distributed normally, with the ...
- math - 35 yrs ago babies are born here hospital celebrated the births of the ...
- statistics - The average weight of all newborn babies at Dearborn Hospital was ...
- statistics, probability - It has been found out that the probability that a ...
- Statistics - In an analysis of test results from the YSORT gender selection ...
- Statisitics:Standard Deviation of Population and o - Standard Deviation of ...
- statistics - Ignoring twins and other mutiple births, assume babies born at a ...
- statistics - The weight of 14 healthy newborn children was measured. The sample...
- Math - An all girl college began enrolling boys in 2005. By 2012 the ratio of ...