Math Is Fun Forum

Hi guys, I have some more questions, could anyone help with these? thanks in advance.

1.The test statistic in a left tailed test is z = -1.25

2. The test statistic in a left tailed test is z = 1.75

3. With H1: p = (equal sign crossed) 0.707, the test statistic is z = - 2.75

4. With H1: p < 0.777, the test statistic is z = - 2.95

5. Random guesses are made for 50 SAT multiple choice questions, so n = 50 and p = 0.2

6. 300 subjects are tested and the probability of a positive result is 0.48, so n = 300 and p = 0.48

7. The midterm exam in nursing course consists of 75 true/false questions. Assume that unprepared student makes random guesses for each of the questions.

8. In the US 40% of the population have brown eyes. If 14 people are randomly selected, find the probability that at least 12 of them have brown eyes. Is it unusual to select 14 people and randomly select 12 that have brown eyes?

9. Ten peas are generated from parents having the green/yellow pair of genes, so there is 0.75 probability that an individual pea will have a green pod. Find the probability that among the 10 offspring peas, at least 9 have green pods. Is it unusual or not.

10.  finding probability:
Z0.05 ?

P (-1.96 < z < 1.96) ?

P (z < - 2.575 or z > 2.575) ?

hi Bobbym and gAr, thanks for the response, appreciate it.

Bobbym how may I contact you to make money transfer?

Thanks for reply Bobbym and apologies for breaking the rules. I didn't want to post them all like this because it takes too much space. Appreciate any input.

1. Among companies doing bridge construction, 80% test employees for substance abuse. A study involves the random selection of 10 such companies. Find the probability that exactly 5of the 10 companies test for substance abuse (assume binomial distribution)

2. Among companies doing bridge construction, 80% test employees for substance abuse (see above). For the group of 10 companies, find the mean and standard deviation for the number (among 10) that test for substance abuse.

3. a) A set of data items is normally distributed with a mean of 60. Convert the data item x=56 to a z-score, if the standard deviation is 4.
   b) A set of data items is normally distributed with a mean of 500 and a standard deviation of 70. Find the data item in this distribution that corresponds to the z-score z= - 1.5

4. The tire corporation claims that the useful life of its tire is normally distributed with a mean life of 28,000 miles and a standard deviation of 4000 miles. What percentage of the tiers are expected to last more than 35,000 miles?

5. The number of major earthquakes is a year is approximately normally distributed with a mean of 20.8 and a standard deviation of 4.5. Find the probability that in a given year there will be between 18 and 23 earthquakes.

6. Birth weights in the united states are normally distributed with a mean of 3420 g and a standard deviation of 495 g. If a hospital plans to set up special observation conditions for the lightest 2% of babies, what weight is used for the cut - off seperatng the lighest 2% from others.

7. Using the Central Limit Theorem that women's heights are normally distributed with a mean of 63.6 in. and a standard deviation of 2.5 in.

a) If a 1 woman is randomly selected, find the probaility that the height is less than 64 in.

b) If 36 women are randomly selected, find the probability that they have a mean height less than 64 in.

8. Find the critical value Za/2 that corresponds to a 98% confidence level.

9. Use sample data and confidence level to construct the confidence interval estimate of the population proportion p: n = 2000, x = 400, 95% confidence.

10. Use the margin of error E= 0.5 in, confidence level 95% and population standard deviation Q = 2.5 in to find the minimum sample size required to estimate an unknown population mean.

11. (Show the work).
A professor has found that the grades on the statistical final are normally distributed with a mean of 72 and a standard deviation of 12.5. The top 8% of the class will receive an A; the next 20%, a B; the next 42%, a C; the next 18%, a D; and the bottom 12%, an F.
What avarage must you obtain to pass the course? (You'll need a D or better)