statistics PLEASE!! HURRY

danu3 · Aug 3, 2004

Okay I have got to have these done by tomorrow, I am lacking sleep and I have been working on the same couple problems for like 7 hours now. If ANY of you can just show me how to do these I will be gratefull forever. ready?
1.If a normally distributed population has a mean of 100 and standard deviation of 10, then 2.5 % of the value lie below what value?

I can't gurantee that this is right since I have not done this in ages.

Here is the rational and you'll be the judge.

A 2 SD will cover 95.44% of the bell curve. 2.5% in the problem is 5.0% (2.5X 2 because you have 2.5% on the right tail and 2.5% on the left tail).

So approximately you have 2 SD here. It is asking for 2.5% below, so it is asking for the left tail of the 2.5%. Each SD is 10 and you have 2 SD so you get 20. So 100-20 = 80. So my guess is there are only 2.5% of the value which lies below 80. Now if you need exactly 5%, I forgot how you do it, there is a formula or a table you should be able to look up.

Don't know if this helps.

-Dan

danu3 · Aug 3, 2004

Ok, I looked up an old table. 2.5% is 1.96 SD.

so you have 10 X 1.96 = 19.6

100 - 19.6 = 80.4

So 2.5% of the value is under 80.4. Again, no gurantee that this is right. Look at my explanation to see if it make sense. If not, don't use it because I have not done this in ages.

-Dan

danu3 · Aug 3, 2004

2.An advertising campaign for a new product is targeted to make 20% of the product. After the campaign a random sample of 200 adults in the metro area is obtained.
What is the probability that
A) 30 or less adults are aware of the product
B)35 or more are aware of the product
3.The quality control manager of Stevie's Cookies is inspecting batches of chocolate chip cookie. When the production process is in the mean number of chocolate chip per cookie is 5.00. What is the probability that for a particular cookie there are...
a) more than 6 chocolate chips in the cookie?
b) 2 or fewer chips in the cookie.

For question 3, are there something missing here? All we have is the mean. I don't think you can figure out the probability if all you have is the mean. You need some other info like the SD will help.

Question number 2, I am totally confused. What do they mean to target 20% of the product?

-Dan

AlishaNHayzley · Aug 5, 2004

Thanks so much, I really appreciate the time.