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Nedd help in some statistic questions

kaylor koh

New member
Joined
Sep 20, 2009
Messages
12
Hi Im trying to solve some statistics question, but there are some that I'm unable to solve. Please help. Thank you

1.Find the area under the standard normal curve between z = 1.5 and z = 2.5

The answer I got is 0.927, but it seems wrong.
I used -1.5 and 2.5
So I got 0.9938-0.0668=0.927

2.(I have absolutly no idea for this quest)
The local lottery sets up a game wherein a player has a chance of collecting $750.
The player must choose a 3-digit number and if it matches, the player receives $750
Remember, 000 is a 3-digit number for lottery draws.
It costs $1 to play the game.
What is each player's expected profit (or loss).

3.0.5 of all college students like the idea of a new curriculum.
If we select 93students (ASSUME INDEPENDENCE), what is the Standard Deviation of the Probability Distribution that would list the number of students (from 0 to 93) and the probability of each

4.A tire company finds the lifespan for one brand of its tires is normally distributed with a mean of 49,300 miles and a standard deviation of 6000 miles. If the manufacturer is willing to replace around 10% of the tires as unsatisfactory performers, what should be the approximate number of miles for a warranty?

5.The probability Mary will receive an A in a class is 0.49.
Assuming independence, if she is taking 5 classes this semester, calculate the probability she will receive exactly 3 A's.

The answer I got is 0.3060 using the bio formula

6.test scores are Normally Distributed with a mean of 73 and a Standard Deviation of 10.
Calculate the z-score of a test score of 49

Answer: 0.0082

7.A mail-order company receives an average of five orders per 500 solicitations. If it sends out 100 advertisements, find the probability of receiving at least two orders

Answer:0.1839 using poisson rule
 

barson90

New member
Joined
Oct 2, 2009
Messages
20
For number one

(z = 2.5) minus (z = 1.5) equals
0.9938 minus 0.9332

0.0606
 

wjm11

Senior Member
Joined
Nov 13, 2004
Messages
1,417
2.(I have absolutly no idea for this quest)
The local lottery sets up a game wherein a player has a chance of collecting $750.
The player must choose a 3-digit number and if it matches, the player receives $750
Remember, 000 is a 3-digit number for lottery draws.
It costs $1 to play the game.
What is each player's expected profit (or loss).
First, there are 1000 3-digit numbers, so the chance of guessing the correct one is 1/1000 = .001. Multiply this chance of winning by the amount one win’s. Second, you always lose $1 just to play. Expected loss:

(.001)($750) - $1 = -$.25
 
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