Statistics
posted by Maria B .
According to a recent survey, 75% of all customers will return to the same grocery store. Suppose 8 customers are selected at random:
A) What is the probability that exactly five of the customers will return?
B) What is the profability that all 8 will return?
C) What is the probability that at least on will return?
D) How many customers would be expected to return to the same store?
E) Calculate the variance in the number of customers returning to the same store?
F) Determine the standard Deviation.

1. A researcher is interested in whether students who attend private high schools have higher average SAT Scores than students in the general population. A random sample of 90 students at a private high school is tested and and a mean SAT score of 1030 is obtained. The average score for public high school student is 1000 (รณ= 200). Is this a one or two tail test and why?

The key to determining onetailed or twotailed tests is in the problem. Note the first sentence. This tells you the test is onetailed because the word "higher" will translate to "greater than" in the alternate hypothesis. Onetailed tests show a specific direction. If the problem was just looking for a difference in either tail, then the test would be twotailed.
I hope this will help. 
According to recent survey 75% of all customers will return yo the same grocery store. Suppose eight customers are selected at random, what
is the probability that:
exactly five of the customers will return?
all eight will return?
At least seven will return?
At least one will returns?
How many customers would be expected to return to the same store?