Thread: Statistics Help

I need help with my statistics homework. I have about 6 questions. Can someone please help?

1. Find the probability of obtaining exactly 2 heads in 4 tosses of a fair coin? Also find the mean and variance. This is an experiment with replacement.

2. The weight of a grapefruit from a large shipment averages 15 oz. with a standard deviation of 2 oz. If these weights are normally distributed and if a grapefruit is picked at random, what is the probability that it will weigh between 13 and 14 oz.?

3. If an urn contains 4 green balls and 3 black balls what is the probability of drawing 3 black balls in a sample size 3 drawn without replacement?

4. Records indicate that 30 % of all students on a university campus are female. Also, 20% of the females are "A" students, plus 70% of the males are "A" students. If an "A" student is selected at random, whta is the probability that the student is female?

5. Two cards are drawn from a deck of 52 cards. Calculate the probability that the draw will include an ace and a nine.

6. A sample of 49 units are taken randomly from a batch of items. The mean cost per unit is $10 with a standard deviation of $3. Construct the 92% confidence interval estimate for M.

Thank you.

I tutor in our Math Dept's math lab, and one of the things we are learning to NOT say to a student is "Oh this is easy!" because it can be misconstrued a certain way; but dear god in heaven man - these problems are BASIC fundamentals. I mean, have you even taken a crack at solving any of them? About the only one that you couldn't write the answer straight down in two lines is #4 and #6.

I will certainly help, but when I see a mass of problems like this, with zero information on what you know, or what you've tried - I'm inclined to not assist.

Actually, I did problems 1,3,4,6. This is a graded homework assignment. I want to make sure I have the correct answers and that I am doing my calculations correctly.

Thank you.

Statgerm

For #2, what have you tried. This is a "normal distribution" problem, so it follows a clear cut model. If your mean is 15oz, and standard deviation of 2oz, then what percentage of values will be 13oz or less? What percentage of values will be 14oz or less? Knowing this, you should be able to find the probability that your grapefruit weight lies between 13 and 14 ounces.

For #5, how many combinations of two cards will include an ace or a 9? How many two card combinations are there out of 52 cards?