STATS homework, check my answers please?

Thank you for looking, I would appreciate if someone could check the first and third answers (***) and possibly help me go about solving the second one? Thanks so much.





What about normal distribution is NOT true?


a.Theoretically, the mean, median, and mode are the same


b. bout 2/3 of observations fall w/in 1 std dev from mean. ***


c. its a discrete prob. distribution.


d. parameters are the mean %26amp; std dev.





The chairman of a stats dept in a college believes that 65% of the dept's grad. assistantships are given to intnl students. A random sample of 60 grad assistants is taken. Find the expected value and the standard error of the sampling distribution of p. (assume 65% is correct). ??help??





Given that Z is a standard normal random variable, a negative value z indicates that:


a.the value z is to the left of the mean. ******


b.the value z is to the right of the median.


c.the standard deviation of Z is negative.


d.the area between zero and z is negative.

STATS homework, check my answers please?
1. Your answer is incorrect. According to the "empirical rule" about 68% of data will fall within 1 std dev from the mean - 68% is not too far from 2/3. The correct answer is "c" - the normal is a continuous and not a discrete probability distribution.





2. Does "p" mean proportion here (in this case it is hypothesized to be 0.65). Often we talk about the distribution of X where X is the number of "successes" (in this case it would be the number of grad assistantships given to intl students). In the latter case X follows a binomial distribution with parameters n=60 and p=0.65.


E(X) = np = 60(0.65) = 39


sd(X) = sqrt(np(1-p)) = sqrt(60(0.65)(0.35)) = 3.6946 approximately.





3. You have this correct.