Explore BrainMass

Normal Distribution

What percentage of this model radio will last longer than 9.5 years?

1) What percentage of this model radio will last longer than 9.5 years? 2) Suppose the manufacturer guarantees the radio for 8 years. What percentage of radios will have to be replaced? 3) Suppose the manufacturer is willing to replace only 2% of this model radio. What should be the length of the guarantee?

Normally dist with mean and SD

Nurses saleries are Normally distributed with mean of 35,000 and standard deviation$1700. A. What is the probability that a nurse earn more than $36,000? B. What is the probality that a group of 10 nurses have mean salary greater than $36,000? c. What salary does a nurse need to earn to have a salary in the top 25% of nurses'

Confidence Limits

A pollster conducted a survy of voters' opinions on a local school bond issue. What would the 95 percent confidence limits be if 53 percent of 1000 people sampled were in favor of the school bond issue? What would the 99 percent confidence limits be for the same sample? I have SPSS 11.0 here. Can I enter this info into it and

3584- distribution P(z<, = or >z)

I need some serious explanation. I cannot even understand what to study for the frist 6 questions on the test about the formula I posted in this subject line. The book I am using is Elementary Statistics by mario F. Triola. 8th edition. Here is what I am to study: Students will have 2 hours to answer 20 exam questions.

Show that for all &#961; and v...

1. (a) Show that if Z1 and Z2 are independent standard normal random variables, then for all &#961; (correlation), Z1 and &#961;Z1+sqrt(1-&#961;2)*Z2 are standard normal with correlation &#961;. (b) Show that for all &#961; and v, T1 = (Z1)/sqrt(X/v)and T2 = (Z2)/sqrt(X/v) have correlation &#961;, where Z1and Z2 are standa

Normal Distribution problem

The amounts dispensed by a cola machine follow the normal distribution with a mean of 7 ounces and a standard deviation of 0.10 ounces per cup. How much cola is dispensed in the largest 1 percent of the cups?

Hypothesis in statistics

A light bulb manufacturer advertises that the average life for their light bulbs is 800 hours. A random sample of 15 of their light bulbs resulted in the following data, in hours; 990 841 953 612 727 800 686 594 835 897 943 791 750 667 723 Assume that the bulb life is normally distributed. At the 10% significance level, do

Estimation using Normal Distribution

A random sample of 55 adults in a certain country showed an average height of six feet (72 inches) for adults. Statistics show the population standard deviation to be 3.40 inches. Calculate the 95% confidence interval for the mean height of the adult population.

What inventory levels to carry? Simulation? Optimization?

We are asked (ideally) to use Crystal Ball (CB), an Excel add-in, or Excel itself to do this inventory problem. CB would be ideal, but we can use just plain-old Excel if it can do what needs to be done. I see this as a simulation or maybe optimization problem, but not sure how to tackle it. Given historical data on deman

Probability Distributions: Normal Distribution

It is known that the IQ scores of workers in a certain company are normally distributed with a standard deviation of ten. If 0.13% of the workers have IQ's in excess of 130 calculate the mean IQ.

Probability Distributions: Normal Distribution

According to the census, the average age of men marrying for the first time is 24 years. Assume ages of men are normally distributed with a standard deviation of three years. A) What is the probability that a man being married for the first time is older than 26 years? B) Before what age do 95% of men who marry for the first t

Probability Distributions: Normal Distribution

Foreign service employees receive housing allowances when posted abroad. These allowances average $30000 annually. Assume that a normal distribution applies and the standard deviation is $5000. A) What is the probability that a diplomat will receive a housing allowance exceeding $35000? B) What is the probability that a diplom

Normal (z) Distributions- In grading Oranges into "A","B" and "C", a large orchard uses weights to distinguish Oranges. If the day's pick shows 16.6% are grade "A" and 6.68% are grade "C", determine the Mean and Standard Deviation.

In grading Oranges into "A","B" and "C", a large orchard uses weights to distinguish Oranges. Any Orange weighing more than 2 ounces is classified as grade "A", while an Orange weighing less than 0.75 ounces is classified as grade "C". If the day's pick shows 16.6% are grade "A" and 6.68% are grade "C", determine the Mean and St

Data rejection following normality tests

Using the Anderson-Darling test for Normality it has been determined that three sets of data "RelHum" (Relative Humidity), "Rain" (Average Rainfall), and "SO2Pot", (SO2 Pollution Potential) all FAIL the test even following log and square root transformation. How do I reject data points in order to make these data sets normal

Sampling distributions of estimates

Consider an acceptance-sampling scheme in which a factory takes delivery of a batch of components if a random sample of 400 components contains fewer than M defectives. Otherwise the batch is returned tot he supplier. Suppose the factory manager wants to set M so that there is no more than a 10% risk of accepting a batch that

Normal Distribution

Assume that X follows normal distribution N(12,4), find a such that P(X>a)=0.5

Mean and variance

7) suppose the average weight of an item labeled 16 ounces actually has mean 17 ounces and variance 4 (ounce^2). What is the approximate probability that the combined weight of 25 items exceeds 445 ounces? What theorem is useful in answering this question?

Normal distribution

A very large number of fish are swimming in a lake. Their weights are normally distributed with mean 1.30kg and a standard deviation 0.40kg. Fish caught with weights less than 0.5kg have to be thrown back. a) If an angler catches a randomly selected fish, what is the probability that the fish has to be thrown back? b) find

Normal distribution

A university professor keeps records of his travel time while he is driving between his home and the university. Over a long period of time he has found that his morning travel times are approx Normally distributed with a mean of 31 minutes and a standard deviation of 3.0 minutes;his return journey in the evening is similarly d

Joint Distributions (normal distributions)

Tim has two more problems to solve on his test, but he doesn't know how long it will take to finish them. He assigns mutually irrelevant normal distributions to the times, assigning a mean of 35 minutes to the first problem and 30 minutes to the second problem. He assigns a 95% chance that the first problem will take 35+-15 minu

Normal distribution and percentiles

True or false: It is not possible for the score in a distribution, not necessarily normal, which ranks as the 90th percentile to also be the mode for the distribution.

Normal Distribution

In a production run of 40 of a particular model of radiation detector, there are four which have defective circuits. If a sample of three of these is chosen without replacement, what is the probability that all three will be defective?

Normal distribution, standard deviation and mean

True or false: When the variable is normally distributed, the sample size is less than 30, and the population standard deviation is known, then the t distribution must be used to find confidence intervals for the mean.

Normal Distribution

VISA reported with 95% confidence that 19% of those surveyed used checks to pay for purchases. If 1478 people participated in the survey, what was the percentage of error?

Normal Distribution

A tornado has blown through a section of Collinsville. The insurance adjuster wants to estimate the average claim to within $500. If the standard deviation is believed to be $1600 and the company wants to be 99% sure of their figures, how large a sample must be taken?

Normal distribution and significance levels

True or false: A retailer wants to estimate with 99% confidence the number of people who buy at his store. A previous study showed that 15% of those interviewed had shopped at his store. He wishes to be accurate within 3% of the true proportion. The minimum sample size necessary would be 940.

Normal distribution, standard deviation and mean

If IQ scores on a Stanford-Binet Test are normally distributed with a mean of 100 and a standard deviation of 15, then about how many people in a randomly chosen million would be expected to score at 160 or above? (This was at one time the break off score for the "genius" designation.) a) 47 b) 32 c) 16