TEST 2                                                       Prof. VanderHoff
Spring 2004                                                            Econ 231
Full credit requires that all work be shown on this paper.
1. [20] Use the following data to make a 90% confidence interval for
the population mean.




3. [10] What are the following probabilities?.

Z=0


-2.31 < Z < -1.35


Z > 1.54


5.[10] Calculate the probabilities for X.   The mean of X is 50 and the standard deviation is 10.


 X > 32



 X > 60



 32< X < 72
6. [5] Calculate the probability of 3 A's in 4 tests, if the probability of an A is 1/3.






7. [5] What is the probability of 6 or 7 correct answers on a test with 11 questions if the
probability of a correct answer is .4?




8. [10] Estimate the population mean and standard deviation with the following data.

-1 
7 
6 
0 
3 
 




9. [10]] For  a sample size of 25 from a distribution with a mean of  40 and a standard deviation
of 8, calculate:
probability ( 38 < sample mean < 41).






10. [10]  The probability a student goes to Florida on SPRING BREAK is .6.  For a group of 50
students, what  is the probability that 25 or more students go?