View Full Version : Statistics- confidence level
Nezza
May 9, 2008, 10:18 PM
Suppose that the population of the scores of all high school seniors that took the SAT-M (SAT math) test this year follows a normal distribution, with mean m and standard deviation s = 100. You read a report that says, On the basis of a simple random sample of 100 high school seniors that took the SAT-M test this year, a confidence interval for m is 512.00 ± 25.76. The confidence level for this interval is:
a:over 99.9%
b: 95%
c.99%
d: 90%
galactus
May 10, 2008, 04:38 AM
Your mission is to find the z-score that corresponds with your confidence interval.
E=z\cdot\frac{\sigma}{\sqrt{n}}
You have E=25.76, \;\ {\sigma}=100, \;\ n=100
Plug them into the formula and solve for z. Then, look it up in the z-table.
Nezza
May 10, 2008, 10:29 AM
Thank you soooo much!
galactus
May 10, 2008, 10:30 AM
If it was helpful, please click on 'rate this answer'.
Nezza
May 10, 2008, 10:44 AM
Galactus,
What about this one, I THINK THE ANSWER IS b, BUT I'M NOT SURE
A deck of ten cards consists of five red and five black cards. The cards are shuffled and I choose one at random, observe its color, and replace it in the set. The cards are thoroughly reshuffled, and I again choose a card at random, observe its color, and replace it in the set. This is done a total of four times. Let X be the number of red cards observed in these four trials. The random variable X has which of the following probability distributions?
a: the binomial distribution with parameters n=4 and p=1
b: the uniform distribution on 0,1,2,3,4
c: the normal distribution with mean 2 and variance 1
d: none of the above
Nezza
May 15, 2008, 01:13 PM
The weights of medium oranges packaged by an orchard are normally distributed with a mean of 14 oz. and a standard deviation of 2 oz. The weights of large oranges packaged by this orchard are normally distributed with a mean of 18 oz. and a standard deviation of 3 oz. If we select a medium packaged orange at random and a large packaged orange at random, the probability that the medium orange weighs more than the large orange is
a. 0.0000
b.0.0228
c. 0.0548
d. 0.1335