# Standard deviation and hypothesis testing

1. Sep 10, 2008

### Cutie_Jenny

Hi guys.

Im new at this site so please be nice to me =P. Ive been working on some practice papers for my upcoming end of semester exams. Cant get these two questions out ><. Any help is greatly appreciated

jenny xoxo

1. A sample of 28 students measured their reaction time by recording the distance a dropped ruler fell before they caught it. This was then repeated to see whether a learning effect was present. The mean decrease in drop distance between the two trials was 1.69 cm with standard deviation 1.916 cm. The margin of error for a 95% confidence interval for the mean decrease in drop distance for all students is ____

2. Suppose we are taking samples from a population that has the same numbers of males and females but are concerned the sampling method may be biased. We take a sample of 20 people and test the null hypothesis H0: p = 0.5, where p is the mean proportion of females in a sample produced by the method.
The power of this test to detect a bias at the 5% level if the sampling method actually produces at least 70% females is ____

2. Sep 10, 2008

### Focus

Have you tried solving them? Post some of your working out or specifics in which you struggle on.