Sample Credit Report Explanations
2010
Homework Help for Statistics Class (Standard Deviation & Probabilities)?
I e-mailed my professor, but I`m unsure if he would be able to get back to me before the assignment is due. No answers are needed (unless you want to give one), just an explanation of how to complete the problem. Thanks!!
The registrar of a large university knows that 28% of the students come to college with credit for an advance placement (AP) course. The registrar is going to conduct interviews with 100 students regarding their experiences at the university. Depending on which students are chosen, the proportion of students in the sample that have AP credit may vary.
Note: Report your answers to 3 decimal places.
In this situation what is the standard deviation of the sample proportion of students who have taken an AP course?
In a sample of 100 students, what is the probability that over 33% of the sample has AP credit?
In a sample of 200 students what is the probability that over 33% of the sample had AP credit?
standard deviation of the sample proportion of students who have taken an AP course is sqrt [ p(1-p) /n ]
where p=0.28 and n=100
Find p(1-p)/n and take its square root.
P( x > 0.33) = P( z > (0.33-0.28) / se) , where se is the standard error of the proportion computed before.
Use the Normal probability table to compute this probability.
Repeat with n=200 instead of 100
Sample proportion phat = 0.33
Variance of proportion = p*(1-p)/n
= 0.28(0.72)/200 =0.001008
S.D. of p is 0.0317
Z = ( 0.33 – 0.28 ) / 0.0317 = 1.5749
P( z > 1.5749) should be computed from the Normal probability table.
=0.0582
Sample Beat 13
Comment