Question
One term at the University of California, Irvine, 400 studentstook the final in Statistics. Their scores averaged 65.3 out of100, and the SD was 25. Now (400) * 25 = 500, 500/400 = 1.25 Is 65.3 ± 2.5 a 95% confidence interval? If so, forwhat? If not, why not? Explain. One term at the University of California, Irvine, 400 studentstook the final in Statistics. Their scores averaged 65.3 out of100, and the SD was 25. Now (400) * 25 = 500, 500/400 = 1.25 Is 65.3 ± 2.5 a 95% confidence interval? If so, forwhat? If not, why not? Explain.
Explanation / Answer
standard error, e = SD/n = 25/400 = 25/20 =1.25 mean, = 65.3 for 95 % confidence, z = 1.96 now confidence interval = ± z e = 65.3 ±1.96 x 1.25 = 65.3 ± 2.45